Methods and compositions for treating hepatitis C virus

ABSTRACT

A method and composition for treating a host infected with hepatitis C comprising administering an effective hepatitis C treatment amount of a described 1′, 2′ or 3′-modified nucleoside or a pharmaceutically acceptable salt or prodrug thereof, is provided.

FIELD OF THE INVENTION

This invention is in the area of pharmaceutical chemistry, and is inparticular, is a compound, method and composition for the treatment ofhepatitis C virus. This application claims priority to U.S. provisionalapplication No. 60/206,585, filed on May 23, 2000.

BACKGROUND OF THE INVENTION

The hepatitis C virus (HCV) is the leading cause of chronic liverdisease worldwide. (Boyer, N. et al. J. Hepatol. 32:98-112, 2000). HCVcauses a slow growing viral infection and is the major cause ofcirrhosis and hepatocellular carcinoma (Di Besceglie, A. M. and Bacon,B. R., Scientific American, October: 80-85, (1999); Boyer, N. et al. J.Hepatol. 32:98-112, 2000). An estimated 170 million persons are infectedwith HCV worldwide. (Boyer, N. et al. J. Hepatol. 32:98-112, 2000).Cirrhosis caused by chronic hepatitis C infection accounts for8,000-12,000 deaths per year in the United States, and HCV infection isthe leading indication for liver transplant.

HCV is known to cause at least 80% of posttransfusion hepatitis and asubstantial proportion of sporadic acute hepatitis. Preliminary evidencealso implicates HCV in many cases of “idiopathic” chronic hepatitis,“cryptogenic” cirrhosis, and probably hepatocellular carcinoma unrelatedto other hepatitis viruses, such as Hepatitis B Virus (HBV). A smallproportion of healthy persons appear to be chronic HCV carriers, varyingwith geography and other epidemiological factors. The numbers maysubstantially exceed those for HBV, though information is stillpreliminary; how many of these persons have subclinical chronic liverdisease is unclear. (The Merck Manual, ch. 69, p. 901, 16th ed.,(1992)).

HCV has been classified as a member of the virus family Flaviviridaethat includes the genera flaviviruses, pestiviruses, and hapaceiviruseswhich includes hepatitis C viruses (Rice, C. M., Flaviviridae: Theviruses and their replication. In: Fields Virology, Editors: Fields, B.N., Knipe, D. M., and Howley, P. M., Lippincott-Raven Publishers,Philadelphia, Pa., Chapter 30, 931-959, 1996). HCV is an enveloped viruscontaining a positive-sense single-stranded RNA genome of approximately9.4 kb. The viral genome consists of a 5′ untranslated region (UTR), along open reading frame encoding a polyprotein precursor ofapproximately 3011 amino acids, and a short 3′ UTR. The 5′ UTR is themost highly conserved part of the HCV genome and is important for theinitiation and control of polyprotein translation. Translation of theHCV genome is initiated by a cap-independent mechanism known as internalribosome entry. This mechanism involves the binding of ribosomes to anRNA sequence known as the internal ribosome entry site (IRES). An RNApseudoknot structure has recently been determined to be an essentialstructural element of the HCV IRES. Viral structural proteins include anucleocapsid core protein (C) and two envelope glycoproteins, E1 and E2.HCV also encodes two proteinases, a zinc-dependent metalloproteinaseencoded by the NS2-NS3 region and a serine proteinase encoded in the NS3region. These proteinases are required for cleavage of specific regionsof the precursor polyprotein into mature peptides. The carboxyl half ofnonstructural protein 5, NS5B, contains the RNA-dependent RNApolymerase. The function of the remaining nonstructural proteins, NS4Aand NS4B, and that of NS5A (the amino-terminal half of nonstructuralprotein 5) remain unknown.

A significant focus of current antiviral research is directed toward thedevelopment of improved methods of treatment of chronic HCV infectionsin humans (Di Besceglie, A. M. and Bacon, B. R., Scientific American,October: 80-85, (1999)). Currently, there are two primary antiviralcompounds, Ribavirin and interferon-alpha, which are used for thetreatment of chronic HCV infections in humans.

Treatment of HCV Infection with Ribivarin

Ribavirin (1-β-D-ribofuranosyl-1-1,2,4-triazole-3-carboxamide) is asynthetic, non-interferon-inducing, broad spectrum antiviral nucleosideanalog sold under the trade name, Virazole (The Merck Index, 11thedition, Editor: Budavari, S., Merck & Co., Inc., Rahway, N.J., p1304,1989). U.S. Pat. No. 3,798,209 and RE29,835 disclose and claimRibavirin. Ribavirin is structurally similar to guanosine, and has invitro activity against several DNA and RNA viruses includingFlaviviridae (Gary L. Davis. Gastroenterology 118: S104-S114, 2000).

Ribavirin reduces serum amino transferase levels to normal in 40% orpatients, but it does not lower serum levels of HCV-RNA (Gary L. Davis.Gastroenterology 118: S104-S114, 2000). Thus, Ribavirin alone is noteffective in reducing viral RNA levels. Additionally, Ribavirin hassignificant toxicity and is known to induce anemia.

Treatment of HCV Infection with Interferon

Interferons (IFNs) are compounds that have been commercially availablefor the treatment of chronic hepatitis for nearly a decade. IFNs areglycoproteins produced by immune cells in response to viral infection.IFNs inhibit viral replication of many viruses, including HCV, and whenused as the sole treatment for hepatitis C infection, IFN suppressesserum HCV-RNA to undetectable levels. Additionally, IFN normalizes serumamino transferase levels. Unfortunately, the effects of IFN aretemporary and a sustained response occurs in only 8%-9% of patientschronically infected with HCV (Gary L. Davis. Gastroenterology 118:S104-S114, 2000).

A number of patents disclose HCV treatments using interferon-basedtherapies. For example, U.S. Pat. No. 5,980,884 to Blatt et al.discloses methods for retreatment of patients afflicted with HCV usingconsensus interferon. U.S. Pat. No. 5,942,223 to Bazer et al. disclosesan anti-HCV therapy using ovine or bovine interferon-tau. U.S. Pat. No.5,928,636 to Alber et al. discloses the combination therapy ofinterleukin-12 and interferon alpha for the treatment of infectiousdiseases including HCV. U.S. Pat. No. 5,908,621 to Glue et al. disclosesthe use of polyethylene glycol modified interferon for the treatment ofHCV. U.S. Pat. No. 5,849,696 to Chretien et al. discloses the use ofthymosins, alone or in combination with interferon, for treating HCV.U.S. Pat. No. 5,830,455 to Valtuena et al. discloses a combination HCVtherapy employing interferon and a free radical scavenger. U.S. Pat. No.5,738,845 to Inakawa discloses the use of human interferon tau proteinsfor treating HCV. Other interferon-based treatments for HCV aredisclosed in U.S. Pat. No. 5,676,942 to Testa et al., U.S. Pat. No.5,372,808 to Blatt et al., and U.S. Pat. No. 5,849,696.

Combination of Interferon and Ribavirin

The combination of IFN and Ribavirin for the treatment of HCV infectionhas been reported to be effective in the treatment of IFN naive patients(Battaglia, A. M. et al., Ann. Pharmacother. 34:487-494, 2000). Resultsare promising for this combination treatment both before hepatitisdevelops or when histological disease is present (Berenguer, M. et al.Antivir. Ther. 3(Suppl. 3):125-136, 1998). Side effects of combinationtherapy include hemolysis, flu-like symptoms, anemia, and fatigue. (GaryL. Davis. Gastroenterology 118: S104-S114, 2000).

Additional References Disclosing Methods to Treat HCV Infections

A number of HCV treatments are reviewed by Bymock et al. in AntiviralChemistry & Chemotherapy, 11:2; 79-95 (2000).

Several substrate-based NS3 protease inhibitors have been identified inthe literature, in which the scissile amide bond of a cleaved substrateis replaced by an electrophile, which interacts with the catalyticserine. Attwood et al. (1998). Antiviral peptide derivatives, 98/22496;Attwood et al. (1999), Antiviral Chemistry and Chemotherapy 10.259-273;Attwood et al. (1999) Preparation and use of amino acid derivatives asanti-viral agents, German Patent Publication DE 19914474; Tung et al.(1998) Inhibitors of serine proteases, particularly hepatitis C virusNS3 protease, WO 98/17679. The reported inhibitors terminate in anelectrophile such as a boronic acid or phosphonate. Llinas-Brunet et al.(1999) Hepatitis C inhibitor peptide analogues, WO 99/07734. Two classesof electrophile-based inhibitors have been described, alphaketoamidesand hydrazinoureas.

The literature has also described a number of non-substrate-basedinhibitors. For example, evaluation of the inhibitory effects of2,4,6-trihydroxy-3-nitro-benzamide derivatives against HCV protease andother serine proteases has been reported. Sudo, K. et al., (1997)Biochemical and Biophysical Research Communications, 238:643-647; Sudo,K. et al. (1998) Antiviral Chemistry and Chemotherapy 9:186. Using areverse-phase HPLC assay, the two most potent compounds identified wereRD3-4082 and RD3-4078, the former substituted on the amide with a 14carbon chain and the latter processing a para-phenoxyphenyl group.

Thiazolidine derivatives have been identified as micromolar inhibitors,using a reverse-phase HPLC assay with an NS3/4A fusion protein andNS5A/5B substrate. Sudo, K. et al. (1996) Antiviral Research 32:9-18.Compound RD-1-6250, possessing a fused cinnamoyl moiety substituted witha long alkyl chain, was the most potent against the isolated enzyme. Twoother active examples were RD4 6205 and RD4 6193.

Other literature reports screening of a relatively small library usingan ELISA assay and the identification of three compounds as potentinhibitors, a thiazolidine and two benzanilides. Kakiuchi N. et al. J.EBS Letters 421:217-220; Takeshita N. et al., Analytical Biochemistry247:242-246, 1997. Several U.S. patents disclose protease inhibitors forthe treatment of HCV. For example, U.S. Pat. No. 6,004,933 to Spruce etal. discloses a class of cysteine protease inhibitors for inhibiting HCVendopeptidase 2. U.S. Pat. No. 5,990,276 to Zhang et al. disclosessynthetic inhibitors of hepatitis C virus NS3 protease. The inhibitor isa subsequence of a substrate of the NS3 protease or a substrate of theNS4A cofactor. The use of restriction enzymes to treat HCV is disclosedin U.S. Pat. No. 5,538,865 to Reyes et al.

Isolated from the fermentation culture broth of Streptomyces sp., Sch68631, a phenan-threnequinone, possessed micromolar activity against HCVprotease in a SDS-PAGE and autoradiography assay. Chu M. et al.,Tetrahedron Letters 37:7229-7232, 1996. In another example by the sameauthors, Sch 351633, isolated from the fungus Penicillium griscofuluum,demonstrated micromolar activity in a scintillation proximity assay. ChuM. et al., Bioorganic and Medicinal Chemistry Letters 9:1949-1952.Nanomolar potency against the HCV NS3 protease enzyme has been achievedby the design of selective inhibitors based on the macromolecule eglinc. Eglin c, isolated from leech, is a potent inhibitor of several serineproteases such as S. griseus proteases A and B, α-chymotrypsin, chymaseand subtilisin. Qasim M. A. et al., Biochemistry 36:1598-1607, 1997.

HCV helicase inhibitors have also been reported. U.S. Pat. No. 5,633,358to Diana G. D. et al.; PCT Publication No. WO 97/36554 of Diana G. D. etal. There are a few reports of HCV polymerase inhibitors: somenucleotide analogues, gliotoxin and the natural product cerulenin.Ferrari R. et al., Journal of Virology 73:1649-1654, 1999; Lohmann V. etal., Virology 249:108-118, 1998.

Antisense phosphorothioate oligodeoxynucleotides complementary tosequence stretches in the 5′ non-coding region of the HCV, are reportedas efficient inhibitors of HCV gene expression in in vitro translationand IIcpG2 IICV-luciferase cell culture systems. Alt M. et al.,Hepatology 22:707-717, 1995. Recent work has demonstrated thatnucleotides 326-348 comprising the 3′ end of the NCR and nucleotides371-388 located in the core coding region of the HCV RNA are effectivetargets for antisense-mediated inhibition of viral translation. Alt M.et al., Archives of Virology 142:589-599, 1997. U.S. Pat. No. 6,001,990to Wands et al. discloses oligonucleotides for inhibiting thereplication of HCV. PCT Publication No. WO 99/29350 disclosescompositions and methods of treatment for hepatitis C infectioncomprising the administration of antisense oligonucleotides that arecomplementary and hybridizable to HCV-RNA. U.S. Pat. No. 5,922,857 toHan et al. disclose nucleic acids corresponding to the sequence of thepestivirus homology box IV area for controlling the translation of HCV.Antisense oligonucleotides as therapeutic agents have been recentlyreviewed (Galderisi U. et al., Journal of Cellular Physiology181:251-257, 1999).

Other compounds have been reported as inhibitors of IRES-dependenttranslation in HCV. Japanese Patent Publication JP-08268890 of Ikeda Net al.; Japanese Patent Publication JP-10101591 of Kai, Y. et al.Nuclease-resistant ribozymes have been targeted at the IRES and recentlyreported as inhibitors in an HCV-poliovirus chimera plaque assay.Maccjak D. J. et al., Hepatology 30 abstract 995, 1999. The use ofribozymes to treat HCV is also disclosed in U.S. Pat. No. 6,043,077 toBarber et al., and U.S. Pat. Nos. 5,869,253 and 5,610,054 to Draper etal.

Other patents disclose the use of immune system potentiating compoundsfor the treatment of HCV. For example, U.S. Pat. No. 6,001,799 toChretien et al. discloses a method of treating hepatitis C innon-responders to interferon treatment by administering an immune systempotentiating dose of thymosin or a thymosin fragment. U.S. Pat. No.5,972,347 to Eder et al. and U.S. Pat. No. 5,969,109 to Bona et al.disclose antibody-based treatments for treating HCV.

U.S. Pat. No. 6,034,134 to Gold et al. discloses certain NMDA receptoragonists having immunodulatory, antimalarial, anti-Borna virus andanti-Hepatitis C activities. The disclosed NMDA receptor agonists belongto a family of 1-amino-alkylcyclohexanes. U.S. Pat. No. 6,030,960 toMorris-Natschke et al. discloses the use of certain alkyl lipids toinhibit the production of hepatitis-induced antigens, including thoseproduced by the HCV virus. U.S. Pat. No. 5,922,757 to Chojkier et al.discloses the use of vitamin E and other antioxidants to treat hepaticdisorders including HCV. U.S. Pat. No. 5,858,389 to Elsherbi et al.discloses the use of squalene for treating hepatitis C. U.S. Pat. No.5,849,800 to Smith et al discloses the use of amantadine for treatmentof Hepatitis C. U.S. Pat. No. 5,846,964 to Ozeki et al. discloses theuse of bile acids for treating HCV. U.S. Pat. No. 5,491,135 to Blough etal. discloses the use of N-(phosphonoacetyl)-L-aspartic acid to treatflaviviruses such as HCV.

Other compounds proposed for treating HCV include plant extracts (U.S.Pat. No. 5,837,257 to Tsai et al., U.S. Pat. No. 5,725,859 to Omer etal., and U.S. Pat. No. 6,056,961), piperidenes (U.S. Pat. No. 5,830,905to Diana et al.), benzenedicarboxamides U.S. Pat. No. 5,633,388 to Dianaet al.), polyadenylic acid derivatives (U.S. Pat. No. 5,496,546 to Wanget al.), 2′,3′-dideoxyinosine (U.S. Pat. No. 5,026,687 to Yarchoan etal.), benzimidazoles (U.S. Pat. No. 5,891,874 to Colacino et al.).

In light of the fact that the hepatitis C virus has reached epidemiclevels worldwide, and has tragic effects on the infected patient, thereremains a strong need to provide new effective pharmaceutical agents totreat hepatitis C that has low toxicity to the host.

Therefore, it is an object of the present invention to provide acompound, method and composition for the treatment of a host infectedwith hepatitis C virus.

SUMMARY OF THE INVENTION

Compounds, methods and compositions for the treatment of hepatitis Cinfection are described that include an effective hepatitis C treatmentamount of a β-D- or β-L-nucleoside of the Formulas (I)-(XVIII), or apharmaceutically acceptable salt or prodrug thereof.

In a first principal embodiment, a compound of Formula I, or apharmaceutically acceptable salt or prodrug thereof, is provided:

wherein:

-   R¹, R² and R³ are independently H, phosphate (including mono-, di-    or triphosphate and a stabilized phosphate prodrug); acyl (including    lower acyl); alkyl (including lower alkyl); sulfonate ester    including alkyl or arylalkyl sulfonyl including methanesulfonyl and    benzyl, wherein the phenyl group is optionally substituted with one    or more substituents as described in the definition of aryl given    herein; a lipid, including a phospholipid; an amino acid; a    carbohydrate; a peptide; a cholesterol; or other pharmaceutically    acceptable leaving group which when administered in vivo is capable    of providing a compound wherein R¹, R² or R³ is independently H or    phosphate;-   Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴;-   X¹ and X² are independently selected from the group consisting of H,    straight chained, branched or cyclic alkyl, CO-alkyl, CO-aryl,    CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁵;    .and-   R⁴ and R⁵ are independently hydrogen, acyl (including lower acyl),    or alkyl (including but not limited to methyl, ethyl, propyl and    cyclopropyl).

In a second principal embodiment, a compound of Formula II, or apharmaceutically acceptable salt or prodrug thereof, is provided:

wherein:

-   R¹, R² and R³ are independently H; phosphate (including    monophosphate, diphosphate, triphosphate, or a stabilized phosphate    prodrug); acyl (including lower acyl); alkyl (including lower    alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl    including methanesulfonyl and benzyl, wherein the phenyl group is    optionally substituted with one or more substituents as described in    the definition of aryl given herein; a lipid, including a    phospholipid; an amino acid; a carbohydrate; a peptide; a    cholesterol; or other pharmaceutically acceptable leaving group    which when administered in vivo is capable of providing a compound    wherein R¹, R² or R³ is independently H or phosphate; and-   Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴;-   X¹ and X² are independently selected from the group consisting of H,    straight chained, branched or cyclic alkyl, CO-alkyl, CO-aryl,    CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁵; and-   R⁴ and R⁵ are independently hydrogen, acyl (including lower acyl),    or alkyl (including but not limited to methyl, ethyl, propyl and    cyclopropyl).

In a third principal embodiment, a compound of Formula III, or apharmaceutically acceptable salt or prodrug thereof, is provided:

wherein:

-   R¹, R² and R³ are independently H; phosphate (including    monophosphate, diphosphate, triphosphate, or a stabilized phosphate    prodrug); acyl (including lower acyl); alkyl (including lower    alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl    including methanesulfonyl and benzyl, wherein the phenyl group is    optionally substituted with one or more substituents as described in    the definition of aryl given herein; a lipid, including a    phospholipid; an amino acid; a carbohydrate; a peptide; a    cholesterol; or other pharmaceutically acceptable leaving group    which when administered in vivo is capable of providing a compound    wherein R¹, R² or R³ is independently H or phosphate; and-   Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴;-   X¹ and X² are independently selected from the group consisting of H,    straight chained, branched or cyclic alkyl, CO-alkyl, CO-aryl,    CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁵; and-   R⁴ and R⁵ are independently hydrogen, acyl (including lower acyl),    or alkyl (including but not limited to methyl, ethyl, propyl and    cyclopropyl).

In a fourth principal embodiment, a compound of Formula IV, or apharmaceutically acceptable salt or prodrug thereof, is provided:

wherein:

-   R¹, R² and R³ are independently H, phosphate (including mono-, di-    or triphosphate and a stabilized phosphate prodrug); acyl (including    lower acyl); alkyl (including lower alkyl); sulfonate ester    including alkyl or arylalkyl sulfonyl including methanesulfonyl and    benzyl, wherein the phenyl group is optionally substituted with one    or more substituents as described in the definition of aryl given    herein; a lipid, including a phospholipid; an amino acid; a    carbohydrate; a peptide; a cholesterol; or other pharmaceutically    acceptable leaving group which when administered in vivo is capable    of providing a compound wherein R¹, R² or R³ is independently H or    phosphate;-   Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴;-   X¹ is selected from the group consisting of H, straight chained,    branched or cyclic alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro,    bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁵; and-   R⁴ and R⁵ are independently hydrogen, acyl (including lower acyl),    or alkyl (including but not limited to methyl, ethyl, propyl and    cyclopropyl).

In a fifth principal embodiment, a compound of Formula V, or apharmaceutically acceptable salt or prodrug thereof, is provided:

wherein:

-   R¹, R² and R³ are independently H; phosphate (including    monophosphate, diphosphate, triphosphate, or a stabilized phosphate    prodrug); acyl (including lower acyl); alkyl (including lower    alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl    including methanesulfonyl and benzyl, wherein the phenyl group is    optionally substituted with one or more substituents as described in    the definition of aryl given herein; a lipid, including a    phospholipid; an amino acid; a carbohydrate; a peptide; a    cholesterol; or other pharmaceutically acceptable leaving group    which when administered in vivo is capable of. providing a compound    wherein R¹, R² or R³ is independently H or phosphate; and-   Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴;-   X¹ is selected from the group consisting of H, straight chained,    branched or cyclic alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro,    bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁵; and-   R⁴ and R⁵ are independently hydrogen, acyl (including lower acyl),    or alkyl (including but not limited to methyl, ethyl, propyl and    cyclopropyl).

In a sixth principal embodiment, a compound of Formula VI, or apharmaceutically acceptable salt or prodrug thereof, is provided:

wherein:

-   R¹, R² and R³ are independently H; phosphate (including    monophosphate, diphosphate, triphosphate, or a stabilized phosphate    prodrug); acyl (including lower acyl); alkyl (including lower    alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl    including methanesulfonyl and benzyl, wherein the phenyl group is    optionally substituted with one or more substituents as described in    the definition of aryl given herein; a lipid, including a    phospholipid; an amino acid; a carbohydrate; a peptide; a    cholesterol; or other pharmaceutically acceptable leaving group    which when administered in vivo is capable of providing a compound    wherein R¹, R² or R³ is independently H or phosphate; and-   Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴;-   X¹ is selected from the group consisting of H, straight chained,    branched or cyclic alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro,    bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁵; and-   R⁴ and R⁵ are independently hydrogen, acyl (including lower acyl),    or alkyl (including but not limited to methyl, ethyl, propyl and    cyclopropyl).

In a seventh principal embodiment, a compound selected from FormulasVII, VIII and IX, or a pharmaceutically acceptable salt or prodrugthereof, is provided:

wherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹, R² and R³ are independently H; phosphate (including    monophosphate, diphosphate, triphosphate, or a stabilized phosphate    prodrug); acyl (including lower acyl); alkyl (including lower    alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl    including methanesulfonyl and benzyl, wherein the phenyl group is    optionally substituted with one or more substituents as described in    the definition of aryl given herein; a lipid, including a    phospholipid; an amino acid; a carbohydrate; a peptide; a    cholesterol; or other pharmaceutically acceptable leaving group    which when administered in vivo is capable of providing a compound    wherein R¹, R² or R³ is independently H or phosphate;-   R⁶ is hydrogen, hydroxy, alkyl (including lower alkyl), azido,    cyano, alkenyl, alkynyl, Br-vinyl, 2-Br-ethyl, —C(O)O(alkyl),    —C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(lower    alkyl), —O(alkenyl), CF₃, chloro, bromo, fluoro, iodo, NO₂, NH₂,    —NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂; and-   X is O, S, SO₂or CH₂.

In a eighth principal embodiment, a compound of Formulas X, XI and XII,or a pharmaceutically acceptable salt or prodrug thereof, is provided:

wherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹, R² and R³ are independently H; phosphate (including    monophosphate, diphosphate, triphosphate, or a stabilized phosphate    prodrug); acyl (including lower acyl); alkyl (including lower    alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl    including methanesulfonyl and benzyl, wherein the phenyl group is    optionally substituted with one or more substituents as described in    the definition of aryl given herein; a lipid, including a    phospholipid; an amino acid; a carbohydrate; a peptide; a    cholesterol; or other pharmaceutically acceptable leaving group    which when administered in vivo is capable of providing a compound    wherein R¹, R² or R³ is independently H or phosphate;-   R⁶ is hydrogen, hydroxy, alkyl (including lower alkyl), azido,    cyano, alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower    alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl),    —O(alkenyl), chloro, bromo, fluoro, iodo, NO₂, NH₂, —NH(lower    alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂;-   R⁷ is hydrogen, OR³, hydroxy, alkyl (including lower alkyl), azido,    cyano, alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower    alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl),    —O(alkenyl), chlorine, bromine, iodine, NO₂, NH₂, —NH(lower alkyl),    —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂; and,-   X is O, S, SO₂ or CH₂.

In a ninth principal embodiment a compound selected from Formulas XIII,XIV and XV, or a pharmaceutically acceptable salt or prodrug thereof, isprovided:

wherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹, R² and R³ are independently H; phosphate (including    monophosphate, diphosphate, triphosphate, or a stabilized phosphate    prodrug); acyl (including lower acyl); alkyl (including lower    alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl    including methanesulfonyl and benzyl, wherein the phenyl group is    optionally substituted with one or more substituents as described in    the definition of aryl given herein; a lipid, including a    phospholipid; an amino acid; a carbohydrate; a peptide; a    cholesterol; or other pharmaceutically acceptable leaving group    which when administered in vivo is capable of providing a compound    wherein R¹, R² or R³ is independently H or phosphate;-   R⁶ is hydrogen, hydroxy, alkyl (including lower alkyl), azido,    cyano, alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower    alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl),    —O(alkenyl), chloro, bromo, fluoro, iodo, NO₂, NH₂, —NH(lower    alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂; and-   X is O, S, SO₂ or CH₂.

In a tenth principal embodiment the invention provides a compound ofFormula XVI, or a pharmaceutically acceptable salt or prodrug thereof:

wherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹ and R² , are independently H; phosphate (including monophosphate,    diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl    (including lower acyl); alkyl (including lower alkyl); sulfonate    ester including alkyl or arylalkyl sulfonyl including    methanesulfonyl and benzyl, wherein the phenyl group is optionally    substituted with one or more substituents as described in the    definition of aryl given herein; a lipid, including a phospholipid;    an amino acid; a carbohydrate; a peptide; a cholesterol; or other    pharmaceutically acceptable leaving group which when administered in    vivo is capable of providing a compound wherein R¹ or R² is    independently H or phosphate;-   R⁶ is hydrogen, hydroxy, alkyl (including lower alkyl), azido,    cyano, alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower    alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl),    —O(alkenyl), chloro, bromo, fluoro, iodo, NO₂, NH₂, —NH(lower    alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂;-   R⁷ and R⁹ are independently hydrogen, OR², hydroxy, alkyl (including    lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl,    —C(O)O(alkyl), —C(O)O(lower alkyl), —O(acyl), —O(lower acyl),    —O(alkyl), —O(lower alkyl), —O(alkenyl), chlorine, bromine, iodine,    NO₂, NH₂, —NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂;-   R⁸ and R¹⁰ are independently H, alkyl (including lower alkyl),    chlorine, bromine or iodine;-   alternatively, R⁷ and R⁹, R⁷ and R¹⁰, R⁸ and R⁹, or R⁸ and R¹⁰ can    come together to form a pi bond; and-   X is O, S, SO₂ or CH₂.

In a eleventh principal embodiment the invention provides a compound ofFormula XVII, or a pharmaceutically acceptable salt or prodrug thereof:

wherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹ and R² are independently H; phosphate (including monophosphate,    diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl    (including lower acyl); alkyl (including lower alkyl); sulfonate    ester including alkyl or arylalkyl sulfonyl including    methanesulfonyl and benzyl, wherein the phenyl group is optionally    substituted with one or more substituents as described in the    definition of aryl given herein; a lipid, including a phospholipid;    an amino acid; a carbohydrate; a peptide; a cholesterol; or other    pharmaceutically acceptable leaving group which when administered in    vivo is capable of providing a compound wherein R¹ or R² is    independently H or phosphate;-   R⁶ is hydrogen, hydroxy, alkyl (including lower alkyl), azido,    cyano, alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower    alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl),    —O(alkenyl), chloro, bromo, fluoro, iodo, NO₂, NH₂, —NH(lower    alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂;-   R⁷ and R⁹ are independently hydrogen, OR², hydroxy, alkyl (including    lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl,    —C(O)O(alkyl), —C(O)O(lower alkyl), —O(acyl), —O(lower acyl),    —O(alkyl), —O(lower alkyl), —O(alkenyl), chlorine, bromine, iodine,    NO₂, NH₂, —NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂;-   R¹⁰ is H, alkyl (including lower alkyl),. chlorine, bromine or    iodine; alternatively, R⁷ and R⁹, or R⁷ and R¹⁰ can come together to    form a pi bond; and-   X is O, S, SO₂ or CH₂.

In an twelfth principal embodiment, the invention provides a compound ofFormula XVIII, or a pharmaceutically acceptable salt or prodrug thereof:

wherein:

-   Base is a purine or pyrrimidine base as defined herein;-   R¹ and R² independently H; phosphate (including monophosphate,    diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl    (including lower acyl); alkyl (including lower alkyl); sulfonate    ester including alkyl or arylalkyl sulfonyl including    methanesulfonyl and benzyl, wherein the phenyl group is optionally    substituted with one or more substituents as described in the    definition of aryl given herein; a lipid, including a phospholipid;    an amino acid; a carbohydrate; a peptide; a cholesterol; or other    pharmaceutically acceptable leaving group which when administered in    vivo is capable of providing a compound wherein R¹ or R² is    independently H or phosphate;-   R⁶ is hydrogen, hydroxy, alkyl (including lower alkyl), azido,    cyano, alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower    alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl),    —O(alkenyl), chloro, bromo, fluoro, iodo, NO₂, NH₂, —NH(lower    alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂;-   R⁷ and R⁹ are independently hydrogen, OR², alkyl (including lower    alkyl), alkenyl, alkynyl, Br-vinyl, O-alkenyl, chlorine, bromine,    iodine, NO₂, amino, lower alkylamino or di(lower-alkyl)amino;-   R⁸ is H, alkyl (including lower alkyl), chlorine, bromine or iodine;-   alternatively, R⁷ and R⁹, or R⁸ and R⁹ can come together to form a    pi bond;-   X is O, S, SO₂ or CH₂.

The β-D- and β-L-nucleosides of this invention may inhibit HCVpolymerase activity. Nucleosides can be screened for their ability toinhibit HCV polymerase activity in vitro according to screening methodsset forth more particularly herein. One can readily determine thespectrum of activity by evaluating the compound in the assays describedherein or with another confirmatory assay.

In one embodiment the efficacy of the anti-HCV compound is measuredaccording to the concentration of compound necessary to reduce theplaque number of the virus in vitro, according to methods set forth moreparticularly herein, by 50% (i.e. the compound's EC₅₀). In preferredembodiments the compound exhibits an EC₅₀ of less than 25, 15, 10, 5, or1 micromolar.

In another embodiment, the active compound can be administered incombination or alternation with another anti-HCV agent. In combinationtherapy, an effective dosage of two or more agents are administeredtogether, whereas during alternation therapy an effective dosage of eachagent is administered serially. The dosages will depend on absorption,inactivation, and excretion rates of the drug as well as other factorsknown to those of skill in the art. It is to be noted that dosage valueswill also vary with the severity of the condition to be alleviated. Itis to be further understood that for any particular subject, specificdosage regimens and schedules should be adjusted over time according tothe individual need and the professional judgment of the personadministering or supervising the administration of the compositions.

Nonlimiting examples of antiviral agents that can be used in combinationwith the compounds disclosed herein include:

(1) an interferon and/or ribavirin (Battaglia, A. M. et al., Ann.Pharmacother. 34:487-494, 2000); Berenguer, M. et al. Antivir. Ther.3(Suppl. 3):125-136, 1998);

(2) Substrate-based NS3 protease inhibitors (Attwood et al., Antiviralpeptide derivatives, PCT WO 98/22496, 1998; Attwood et al., AntiviralChemistry and Chemotherapy 10.259-273, 1999; Attwood et al., Preparationand use of amino acid derivatives as anti-viral agents, German PatentPublication DE 19914474; Tung et al. Inhibitors of serine proteases,particularly hepatitis C virus NS3 protease, PCT WO 98/17679), includingalphaketoamides and hydrazinoureas, and inhibitors that terminate in anelectrophile such as a boronic acid or phosphonate. Llinas-Brunet et al,Hepatitis C inhibitor peptide analogues, PCT WO 99/07734.

(3) Non-substrate-based inhibitors such as2,4,6-trihydroxy-3-nitro-benzamide derivatives (Sudo K. et al.,Biochemical and Biophysical Research Communications, 238:643-647, 1997;Sudo K. et al. Antiviral Chemistry and Chemotherapy 9:186, 1998),including RD3-4082 and RD3-4078, the former substituted on the amidewith a 14 carbon chain and the latter processing a para-phenoxyphenylgroup;

(4) Thiazolidine derivatives which show relevant inhibition in areverse-phase HPLC assay with an NS3/4A fusion protein and NS5A/5Bsubstrate (Sudo K. et al., Antiviral Research 32:9-18, 1996), especiallycompound RD-1-6250, possessing a fused cinnamoyl moiety substituted witha long alkyl chain, RD4 6205 and RD4 6193;

(5) Thiazolidines and benzanilides identified in Kakiuchi N. et al. J.EBS Letters 421:217-220; Takeshita N. et al. Analytical Biochemistry247:242-246, 1997;

(6) A phenan-threnequinone possessing activity against HCV protease in aSDS-PAGE and autoradiography assay isolated from the fermentationculture broth of Streptomyces sp., Sch 68631 (Chu M. et al., TetrahedronLetters 37:7229-7232, 1996), and Sch 351633, isolated from the fungusPenicillium griscofuluum, which demonstrates activity in a scintillationproximity assay (Chu M. et al., Bioorganic and Medicinal ChemistryLetters 9:1949-1952);

(7) Selective NS3 inhibitors based on the macromolecule elgin c,isolated from leech (Qasim M. A. et al., Biochemistry 36:1598-1607,1997);

(8) HCV helicase inhibitors (Diana G. D. et al., Compounds, compositionsand methods for treatment of hepatitis C, U.S. Pat. No. 5,633,358; DianaG. D. et al., Piperidine derivatives, pharmaceutical compositionsthereof and their use in the treatment of hepatitis C, PCT WO 97/36554);

(9) HCV polymerase inhibitors such as nucleotide analogues, gliotoxin(Ferrari R. et al. Journal of Virology 73:1649-1654, 1999), and thenatural product cerulenin (Lohmann V. et al., Virology 249:108-118,1998);

(10) Antisense phosphorothioate oligodeoxynucleotides (S-ODN)complementary to sequence stretches in the 5′ non-coding region (NCR) ofthe HCV (Alt M. et al., Hepatology 22:707-717, 1995), or nucleotides326-348 comprising the 3′ end of the NCR and nucleotides 371-388 locatedin the core coding region of the IICV RNA (Alt M. et al., Archives ofVirology 142:589-599, 1997; Galderisi U. et al., Journal of CellularPhysiology 181:251-257, 1999);

(11) Inhibitors of IRES-dependent translation (Ikeda N et al., Agent forthe prevention and treatment of hepatitis C, Japanese Patent PublicationJP-08268890; Kai Y. et al. Prevention and treatment of viral diseases,Japanese Patent Publication JP-10101591);

(12) Nuclease-resistant ribozymes (Maccjak D. J. et al., Hepatology 30abstract 995, 1999); and

(13) Other miscellaneous compounds including 1-amino-alkylcyclohexanes(U.S. Pat. No. 6,034,134 to Gold et al.), alkyl lipids (U.S. Pat. No.5,922,757 to Chojkier et al.), vitamin E and other antioxidants (U.S.Pat. No. 5,922,757 to Chojkier et al.), squalene, amantadine, bile acids(U.S. Pat. No. 5,846,964 to Ozeki et al.),N-(phosphonoacetyl)-L-aspartic acid, (U.S. Pat. No. 5,830,905 to Dianaet al.), benzenedicarboxamides (U.S. Pat. No. 5,633,388 to Diana etal.), polyadenylic acid derivatives (U.S. Pat. No. 5,496,546 to Wang etal.), 2′,3′-dideoxyinosine (U.S. Pat. No. 5,026,687 to Yarchoan et al.),and benzimidazoles (U.S. Pat. No. 5,891,874 to Colacino et al.).

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 provides the structure of various non-limiting examples ofnucleosides of the present invention, as well as other knownnucleosides, FIAU and Ribavirin, which are used as comparative examplesin the text.

FIG. 2 is a line graph of the pharmacokinetics (plasma concentrations)of β-D-2′-CH₃-riboG administered to six Cynomolgus Monkeys over timeafter administration.

FIGS. 3 a and 3 b are line graphs of the pharmacokinetics (plasmaconcentrations) of β-D-2′-CH₃-riboG administered to Cynomolgus Monkeyseither intravenously (3 a) or orally (3 b) over time afteradministration.

DETAILED DESCRIPTION OF THE INVENTION

The invention as disclosed herein is a compound, method and compositionfor the treatment of hepatitis C in humans or other host animals, thatincludes administering an effective HCV treatment amount of a β-D- orβ-L-nucleoside as described herein or a pharmaceutically acceptable saltor prodrug thereof, optionally in a pharmaceutically acceptable carrier.The compounds of this invention either possess antiviral (i.e.,anti-HCV) activity, or are metabolized to a compound that exhibits suchactivity.

In summary, the present invention includes the following features:

(a) β-D- and β-L-nucleosides, as described herein, and pharmaceuticallyacceptable salts and prodrugs thereof;

(b) β-D- and β-L-nucleosides as described herein, and pharmaceuticallyacceptable salts and prodrugs thereof for use in the treatment orprophylaxis of an HCV infection, especially in individuals diagnosed ashaving an HCV infection or being at risk for becoming infected by HCV;

(c) use of these β-D- and β-L-nucleosides, and pharmaceuticallyacceptable salts and prodrugs thereof in the manufacture of a medicamentfor treatment of an HCV infection;

(d) pharmaceutical formulations comprising the β-D- or β-L-nucleosidesor pharmaceutically acceptable salts or prodrugs thereof together with apharmaceutically acceptable carrier or diluent;

(e) β-D- and β-L-nucleosides as described herein substantially in theabsence of enantiomers of the described nucleoside, or substantiallyisolated from other chemical entities;

(f) processes for the preparation of β-D- and β-L-nucleosides, asdescribed in more detail below; and

(g) processes for the preparation of β-D- and β-L-nucleosidessubstantially in the absence of enantiomers of the described nucleoside,or substantially isolated from other chemical entities.

I. Active Compound, and Physiologically Acceptable Salts and ProdrugsThereof

In a first principal embodiment, a compound of Formula I, or apharmaceutically acceptable salt or prodrug thereof, is provided:

wherein:

-   R¹, R² and R³ are independently H, phosphate (including mono-, di-    or triphosphate and a stabilized phosphate prodrug); acyl (including    lower acyl); alkyl (including lower alkyl); sulfonate ester    including alkyl or arylalkyl sulfonyl including methanesulfonyl and    benzyl, wherein the phenyl group is optionally substituted with one    or more substituents as described in the definition of aryl given    herein; a lipid, including a phospholipid; an amino acid; a    carbohydrate; a peptide; a cholesterol; or other pharmaceutically    acceptable leaving group which when administered in vivo is capable    of providing a compound wherein R¹, R² or R³ is independently H or    phosphate;-   Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴;-   X¹ and X² are independently selected from the group consisting of H,    straight chained, branched or cyclic alkyl, CO-alkyl, CO-aryl,    CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁵; and-   R⁴ and R⁵ are independently hydrogen, acyl (including lower acyl),    or alkyl (including but not limited to methyl, ethyl, propyl and    cyclopropyl).

In a preferred subembodiment, a compound of Formula I, or apharmaceutically acceptable salt or prodrug thereof, is providedwherein:

-   R¹, R² and R³ are independently H or phosphate (preferably H);-   X¹ is H;-   X² is H or NH₂; and-   Y is hydrogen, bromo, chloro, fluoro, iodo, NH₂ or OH.

In a second principal embodiment, a compound of Formula II, or apharmaceutically acceptable salt or prodrug thereof, is provided:

wherein:

-   R¹, R² and R³ are independently H; phosphate (including    monophosphate, diphosphate, triphosphate, or a stabilized phosphate    prodrug); acyl (including lower acyl); alkyl (including lower    alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl    including methanesulfonyl and benzyl, wherein the phenyl group is    optionally substituted with one or more substituents as described in    the definition of aryl given herein; a lipid, including a    phospholipid; an amino acid; a carbohydrate; a peptide; a    cholesterol; or other pharmaceutically acceptable leaving group    which when administered in vivo is capable of providing a compound    wherein R¹, R² or R³ is independently H or phosphate; and-   Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴;-   X¹ and X² are independently selected from the group consisting of H,    straight chained, branched or cyclic alkyl, CO-alkyl, CO-aryl,    CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁵; and-   R⁴ and R⁵ are independently hydrogen, acyl (including lower acyl),    or alkyl (including but not limited to methyl, ethyl, propyl and    cyclopropyl).

In a preferred subembodiment, a compound of Formula II, or apharmaceutically acceptable salt or prodrug thereof, is providedwherein:

-   R¹, R² and R³ are independently H or phosphate (preferably H);-   X¹ is H;-   X² is H or NH₂; and-   Y is hydrogen, bromo, chloro, fluoro, iodo, NH₂ or OH.

In a third principal embodiment, a compound of Formula III, or apharmaceutically acceptable salt or prodrug thereof, is provided:

wherein:

-   R¹, R² and R³ are independently H; phosphate (including    monophosphate, diphosphate, triphosphate, or a stabilized phosphate    prodrug); acyl (including lower acyl); alkyl (including lower    alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl    including methanesulfonyl and benzyl, wherein the phenyl group is    optionally substituted with one or more substituents as described in    the definition of aryl given herein; a lipid, including a    phospholipid; an amino acid; a carbohydrate; a peptide; a    cholesterol; or other pharmaceutically acceptable leaving group    which when administered in vivo is capable of providing a compound    wherein R¹, R² or R³ is independently H or phosphate; and-   Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴;-   X¹ and X² are independently selected from the group consisting of H,    straight chained, branched or cyclic alkyl, CO-alkyl, CO-aryl,    CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁵; and-   R⁴ and R⁵ are independently hydrogen, acyl (including lower acyl),    or alkyl (including but not limited to methyl, ethyl, propyl and    cyclopropyl).

In a preferred subembodiment, a compound of Formula III, or apharmaceutically acceptable salt or prodrug thereof, is providedwherein:

-   R¹, R² and R³ are independently H or phosphate (preferably H);-   X¹ is H;-   X² is H or NH₂; and-   Y is hydrogen, bromo, chloro, fluoro, iodo, NH₂ or OH.

In a fourth principal embodiment, a compound of Formula IV, or apharmaceutically acceptable salt or prodrug thereof, is provided:

wherein:

-   R¹, R² and R³ are independently H, phosphate (including mono-, di-    or triphosphate and a stabilized phosphate prodrug); acyl (including    lower acyl); alkyl (including lower alkyl); sulfonate ester    including alkyl or arylalkyl sulfonyl including methanesulfonyl and    benzyl, wherein the phenyl group is optionally substituted with one    or more substituents as described in the definition of aryl given    herein; a lipid, including a phospholipid; an amino acid; a    carbohydrate; a peptide; a cholesterol; or other pharmaceutically    acceptable leaving group which when administered in vivo is capable    of providing a compound wherein R¹, R² or R³ is independently H or    phosphate;-   Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴;-   X¹ is selected from the group consisting of H, straight chained,    branched or cyclic alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro,    bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁵; and-   R⁴ and R⁵ are independently hydrogen, acyl (including lower acyl),    or alkyl (including but not limited to methyl, ethyl, propyl and    cyclopropyl).

In a preferred subembodiment, a compound of Formula IV, or apharmaceutically acceptable salt or prodrug thereof, is providedwherein:

-   R¹, R² and R³ are independently H or phosphate (preferably H);-   X¹ is H or CH₃; and-   Y is hydrogen, bromo, chloro, fluoro, iodo, NH₂ or OH.

In a fifth principal embodiment, a compound of Formula V, or apharmaceutically acceptable salt or prodrug thereof, is provided:

wherein:

-   R¹, R² and R³ are independently H; phosphate (including    monophosphate, diphosphate, triphosphate, or a stabilized phosphate    prodrug); acyl (including lower acyl); alkyl (including lower    alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl    including methanesulfonyl and benzyl, wherein the phenyl group is    optionally substituted with one or more substituents as described in    the definition of aryl given herein; a lipid, including a    phospholipid; an amino acid; a carbohydrate; a peptide; a    cholesterol; or other pharmaceutically acceptable leaving group    which when administered in vivo is capable of providing a compound    wherein R¹, R² or R³ is independently H or phosphate; and-   Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴;-   X¹ is selected from the group consisting of H, straight chained,    branched or cyclic alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro,    bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁵; and-   R⁴ and R⁵ are independently hydrogen, acyl (including lower acyl),    or alkyl (including but not limited to methyl, ethyl, propyl and    cyclopropyl).

In a preferred subembodiment, a compound of Formula V, or apharmaceutically acceptable salt or prodrug thereof, is providedwherein:

-   R¹, R² and R³ are independently H or phosphate (preferably H);-   X¹ is H or CH₃; and-   Y is hydrogen, bromo, chloro, fluoro, iodo, NH₂ or OH.

In a sixth principal embodiment, a compound of Formula VI, or apharmaceutically acceptable salt or prodrug thereof, is provided:

wherein:

-   R¹, R² and R³ are independently H; phosphate (including    monophosphate, diphosphate, triphosphate, or a stabilized phosphate    prodrug); acyl (including lower acyl); alkyl (including lower    alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl    including methanesulfonyl and benzyl, wherein the phenyl group is    optionally substituted with one or more substituents as described in    the definition of aryl given herein; a lipid, including a    phospholipid; an amino acid; a carbohydrate; a peptide; a    cholesterol; or other pharmaceutically acceptable leaving group    which when administered in vivo is capable of providing a compound    wherein R¹, R² or R³ is independently H or phosphate; and-   Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴;-   X¹ is selected from the group consisting of H, straight chained,    branched or cyclic alkyl, CO -alkyl, CO-aryl, CO-alkoxyalkyl,    chloro, bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁵; and-   R⁴ and R⁵ are independently hydrogen, acyl (including lower acyl),    or alkyl (including but not limited to methyl, ethyl, propyl and    cyclopropyl).

In a preferred subembodiment, a compound of Formula VI, or apharmaceutically acceptable salt or prodrug thereof, is providedwherein:

-   R¹, R² and R³ are independently H or phosphate (preferably H);-   X¹ is H or CH₃; and-   Y is hydrogen, bromo, chloro, fluoro, iodo, NH₂ or OH.

In a seventh principal embodiment, a compound selected from FormulasVII, VIII and IX, or a pharmaceutically acceptable salt or prodrugthereof, is provided:

wherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹, R² and R³ are independently H; phosphate (including    monophosphate, diphosphate, triphosphate, or a stabilized phosphate    prodrug); acyl (including lower acyl); alkyl (including lower    alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl    including methanesulfonyl and benzyl, wherein the phenyl group is    optionally substituted with one or more substituents as described in    the definition of aryl given herein; a lipid, including a    phospholipid; an amino acid; a carbohydrate; a peptide; a    cholesterol; or other pharmaceutically acceptable leaving group    which when administered in vivo is capable of providing a compound    wherein R¹, R² or R³ is independently H or phosphate;-   R⁶ is hydrogen, hydroxy, alkyl (including lower alkyl), azido,    cyano, alkenyl, alkynyl, Br-vinyl, 2-Br-ethyl, —C(O)O(alkyl),    —C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(lower    alkyl), —O(alkenyl), CF₃, chloro, bromo, fluoro, iodo, NO₂, NH₂,    —NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂; and-   X is O, S, SO₂, or CH₂.

In a first preferred subembodiment, a compound of Formula VII, VIII orIX, or a pharmaceutically acceptable salt or prodrug thereof, isprovided wherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹, R² and R³ are independently hydrogen or phosphate;-   R⁶ is alkyl; and-   X is O, S, SO₂ or CH₂.

In a second preferred subembodiment, a compound of Formula VII, VIII orIX, or a pharmaceutically acceptable salt or prodrug thereof, isprovided wherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹, R² and R³ are hydrogens;-   R⁶ is alkyl; and-   X is O, S, SO₂ or CH₂.

In a third preferred subembodiment, a compound of Formula VII, VIII orIX, or a pharmaceutically acceptable salt or prodrug thereof, isprovided wherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹, R² and R³ are independently hydrogen or phosphate;-   R⁶ is alkyl; and-   X is O.

In a eighth principal embodiment, a compound of Formula X, XI or XII, ora pharmaceutically acceptable salt or prodrug thereof, is provided:

wherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹, R² and R³ are independently H; phosphate (including    monophosphate, diphosphate, triphosphate, or a stabilized phosphate    prodrug); acyl (including lower acyl); alkyl (including lower    alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl    including methanesulfonyl and benzyl, wherein the phenyl group is    optionally substituted with one or more substituents as described in    the definition of aryl given herein; a lipid, including a    phospholipid; an amino acid; a carbohydrate; a peptide; a    cholesterol; or other pharmaceutically acceptable leaving group    which when administered in vivo is capable of providing a compound    wherein R¹, R² or R³ is independently H or phosphate;-   R⁶ is hydrogen, hydroxy, alkyl (including lower alkyl), azido,    cyano, alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower    alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl),    —O(alkenyl), chloro, bromo, fluoro, iodo, NO₂, NH₂, —NH(lower    alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂;-   R⁷ is hydrogen, OR³, hydroxy, alkyl (including lower alkyl), azido,    cyano, alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower    alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl),    —O(alkenyl), chlorine, bromine, iodine, NO₂, NH₂, —NH(lower alkyl),    —NH(acyl), —N(loweralkyl)₂, —N(acyl)₂; and-   X is O, S, SO₂ or CH₂.

In a first preferred subembodiment, a compound of Formula X, XI or XII,or a pharmaceutically acceptable salt or prodrug thereof, is providedwherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹, R² and R³ are independently hydrogen or phosphate;-   R⁶ is alkyl; and-   X is O, S, SO₂ or CH₂.

In a second preferred subembodiment, a compound of Formula X, XI or XII,or a pharmaceutically acceptable salt or prodrug thereof, is providedwherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹, R² and R³ are hydrogens;-   R⁶ is alkyl; and-   X is O, S, SO₂ or CH₂.

In a third preferred subembodiment, a compound of Formula X, XI or XII,or a pharmaceutically acceptable salt or prodrug thereof, is providedwherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹, R² and R³ are independently H or phosphate;-   R⁶ is alkyl; and-   X is O.

In even more preferred subembodiments, a compound of Formula XI, or itspharmaceutically acceptable salt or prodrug, is provided:

wherein:

-   Base is a purine or pyrimidine base as defined herein; optionally    substituted with an amine or cyclopropyl (e.g., 2-amino, 2,6-diamino    or cyclopropyl guanosine); and-   R¹ and R² are independently H; phosphate (including monophosphate,    diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl    (including lower acyl); alkyl (including lower alkyl); sulfonate    ester including alkyl or arylalkyl sulfonyl including    methanesulfonyl and benzyl, wherein the phenyl group is optionally    substituted with one or more substituents as described in the    definition of aryl given herein; a lipid, including a phospholipid;    an amino acid; a carbohydrate; a peptide; a cholesterol; or other    pharmaceutically acceptable leaving group which when administered in    vivo is capable of providing a compound wherein R¹ or R² is    independently H or phosphate.

In a ninth principal embodiment a compound selected from Formula XIII,XIV or XV, or a pharmaceutically acceptable salt or prodrug thereof, isprovided:

wherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹, R² and R³ are independently H; phosphate (including    monophosphate, diphosphate, triphosphate, or a stabilized phosphate    prodrug); acyl (including lower acyl); alkyl (including lower    alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl    including methanesulfonyl and benzyl, wherein the phenyl group is    optionally substituted with one or more substituents as described in    the definition of aryl given herein; a lipid, including a    phospholipid; an amino acid; a carbohydrate; a peptide; a    cholesterol; or other pharmaceutically acceptable leaving group    which when administered in vivo is capable of providing a compound    wherein R¹, R² or R³ is independently H or phosphate;-   R⁶ is hydrogen, hydroxy, alkyl (including lower alkyl), azido,    cyano, alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower    alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl),    —O(alkenyl), chloro, bromo, fluoro, iodo, NO₂, NH₂, —NH(lower    alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂; and-   X is O, S, SO₂ or CH₂.

In a first preferred subembodiment, a compound of Formula XIII, XIV orXV, or a pharmaceutically acceptable salt or prodrug thereof, isprovided wherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹, R² and R³ are independently hydrogen or phosphate;-   R⁶ is alkyl; and-   X is O, S, SO₂ or CH₂.

In a second preferred subembodiment, a compound of Formula XIII, XIV orXV, or a pharmaceutically acceptable salt or prodrug thereof, isprovided wherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹, R² and R³ are hydrogens;-   R⁶ is alkyl; and-   X is O, S, SO₂ or CH₂.

In a third preferred subembodiment, a compound of Formula XIII, XIV orXV, or a pharmaceutically acceptable salt or prodrug thereof, isprovided wherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹, R² and R³ are independently hydrogen or phosphate;-   R⁶ is alkyl; and-   X is O.

In a tenth principal embodiment the invention provides a compound ofFormula XVI, or a pharmaceutically acceptable salt or prodrug thereof:

wherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹ and R² are independently H; phosphate (including monophosphate,    diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl    (including lower acyl); alkyl (including lower alkyl); sulfonate    ester including alkyl or arylalkyl sulfonyl including    methanesulfonyl and benzyl, wherein the phenyl group is optionally    substituted with one or more substituents as described in the    definition of aryl given herein; a lipid, including a phospholipid;    an amino acid; a carbohydrate; a peptide; a cholesterol; or other    pharmaceutically acceptable leaving group which when administered in    vivo is capable of providing a compound wherein R¹ and R² are    independently H or phosphate;-   R⁶ is hydrogen, hydroxy, alkyl (including lower alkyl), azido,    cyano, alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower    alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl),    —O(alkenyl), chloro, bromo, fluoro, iodo, NO₂, NH₂, —NH(lower    alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂;-   R⁷ and R⁹ are independently hydrogen, OR², hydroxy, alkyl (including    lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl,    —C(O)O(alkyl), —C(O)O(lower alkyl), —O(acyl), —O(lower acyl),    —O(alkyl), —O(lower alkyl), —O(alkenyl), chlorine, bromine, iodine,    NO₂, NH₂, —NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂;-   R⁸ and R¹⁰ are independently H, alkyl (including lower alkyl),    chlorine, bromine or iodine; alternatively, R⁷ and R⁹, R⁷ and R¹⁰,    R⁸ and R⁹, or R⁸ and R¹⁰ can come together to form a pi bond; and-   X is O, S, SO₂ or CH₂.

In a first preferred subembodiment, a compound of Formula XVI, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate;. a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently OR², alkyl, alkenyl, alkynyl, Br-vinyl, O-alkenyl,chlorine, bromine, iodine, NO₂, amino, loweralkylamino ordi(loweralkyl)amino; (5) R⁸ and R¹⁰ are independently H, alkyl(including lower alkyl), chlorine, bromine, or iodine; and (6) X is O,S, SO₂ or CH₂.

In a second preferred subembodiment, a compound of Formula XVI, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl, alkenyl, alkynyl,Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo, fluoro, iodo, NO₂,amino, loweralkylamino, or di(loweralkyl)amino; (4) R⁷ and R⁹ areindependently OR²; (5) R⁸ and R¹⁰ are independently H, alkyl (includinglower alkyl), chlorine, bromine, or iodine; and (6) X is O, S, SO₂ orCH₂.

In a third preferred subembodiment, a compound of Formula XVI, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl, alkenyl, alkynyl,Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo, fluoro, iodo, NO₂,amino, loweralkylamino or di(loweralkyl)amino; (4) R⁷ and R⁹ areindependently OR², alkyl, alkenyl, alkynyl, Br-vinyl, O-alkenyl,chlorine, bromine, iodine, NO₂, amino, loweralkylamino ordi(loweralkyl)amino; (5) R⁸ and R¹⁰ are H; and (6) X is O, S, SO₂ orCH₂.

In a fourth preferred subembodiment, a compound of Formula XVI, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl, alkenyl, alkynyl,Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo, fluoro, iodo, NO₂,amino, loweralkylamino, or di(loweralkyl)amino; (4) R⁷ and R⁹ areindependently OR², alkyl, alkenyl, alkynyl, Br-vinyl, O-alkenyl,chlorine, bromine, iodine, NO₂, amino, loweralkylamino, ordi(loweralkyl)amino; (5) R⁸ and R¹⁰ are independently H, alkyl(including lower alkyl), chlorine, bromine, or iodine; and (6) X is O.

In a fifth preferred subembodiment, a compound of Formula XVI, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently OR¹; (5) R⁸ and R¹⁰ are independently H, alkyl (includinglower alkyl), chlorine, bromine or iodine; and (6) X is O, S, SO₂ orCH₂.

In a sixth preferred subembodiment, a compound of Formula XVI, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently OR², alkyl (including lower alkyl), alkenyl, alkynyl,Br-vinyl, O-alkenyl, chlorine, bromine, iodine, NO₂, amino,loweralkylamino, or di(loweralkyl)amino; (5) R⁸ and R¹⁰ are H; and (6) Xis O, S, SO₂, or CH₂.

In a seventh preferred subembodiment, a compound of Formula XVI, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently OR², alkyl (including lower alkyl), alkenyl, alkynyl,Br-vinyl, O-alkenyl, chlorine, bromine, iodine, NO₂, amino,loweralkylamino or di(loweralkyl)amino; (5) R⁸ and R¹⁰ are independentlyH, alkyl (including lower alkyl), chlorine, bromine or iodine; and (6) Xis O.

In a eighth preferred subembodiment, a compound of Formula XVI, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including. lower alkyl); sulfonate ester including alkylor arylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino or di(loweralkyl)amino; (4) R⁷and R⁹ are independently OR²; (5) R⁸ and R¹⁰ are hydrogen; and (6) X isO, S, SO₂ or CH₂.

In a ninth preferred subembodiment, a compound of Formula XVI, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino or di(loweralkyl)amino; (4) R⁷and R⁹ are independently OR²; (5) R⁸ and R¹⁰ are independently H, alkyl(including lower alkyl), chlorine, bromine or iodine; and (6) X is O.

In a tenth preferred subembodiment, a compound of Formula XVI, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H. or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino or di(loweralkyl)amino; (4) R⁷and R⁹ are independently OR², alkyl (including lower alkyl), alkenyl,alkynyl, Br-vinyl, O-alkenyl, chlorine, bromine, iodine, NO₂, amino,loweralkylamino, or di(loweralkyl)amino; (5) R⁸ and R¹⁰ are hydrogen;and (6) X is O.

In an eleventh preferred subembodiment, a compound of Formula XVI, orits pharmaceutically acceptable salt or prodrug, is provided in which:(1) Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino or di(loweralkyl)amino; (4) R⁷and R⁹ are independently OR²; (5) R⁸ and R¹⁰ are hydrogen; and (6) X isO, S, SO₂ or CH₂.

In a twelfth preferred subembodiment, a compound of Formula XVI, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently OR²; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O, S, SO₂,or CH₂.

In a thirteenth preferred subembodiment, a compound of Formula XVI, orits pharmaceutically acceptable salt or prodrug, is provided in which:(1) Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently OR²; (5) R⁸ and R¹⁰ are independently H, alkyl (includinglower alkyl), chlorine, bromine, or iodine; and (6) X is O.

In a fourteenth preferred subembodiment, a compound of Formula XVI, orits pharmaceutically acceptable salt or prodrug, is provided in which:(1) Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently OR², alkyl (including lower alkyl), alkenyl, alkynyl,Br-vinyl, O-alkenyl, chlorine, bromine, iodine, NO₂, amino,loweralkylamino or di(loweralkyl)amino; (5) R⁸ and R¹⁰ are hydrogen; and(6) X is O.

In even more preferred subembodiments, a compound of Formula XVI, or itspharmaceutically acceptable salt or prodrug, is provided in which:

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O;

(1) Base is guanine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O;

(1) Base is cytosine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ andR⁹ are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O;

(1) Base is thymine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O;

(1) Base is uracil; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O;

(1) Base is adenine; (2) R¹ is phosphate; (3) R⁶ is methyl; (4) R⁷ andR⁹ are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O;

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is ethyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O;

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is propyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O;

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is butyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O;

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ ishydrogen and R⁹ is hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X isO;

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is S;

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is SO₂;

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is CH₂;

In a eleventh principal embodiment the invention provides a compound ofFormula XVII, or a pharmaceutically acceptable salt or prodrug thereof:

wherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹ is H; phosphate (including monophosphate, diphosphate,    triphosphate, or a stabilized phosphate prodrug); acyl (including    lower acyl); alkyl (including lower alkyl); sulfonate ester    including alkyl or arylalkyl sulfonyl including methanesulfonyl and    benzyl, wherein the phenyl group is optionally substituted with one    or more substituents as described in the definition of aryl given    herein; a lipid, including a phospholipid; an amino acid; a    carbohydrate; a peptide; a cholesterol; or other pharmaceutically    acceptable leaving group which when administered in vivo is capable    of providing a compound wherein R¹ is independently H or phosphate;-   R⁶ is hydrogen, hydroxy, alkyl (including lower alkyl), azido,    cyano, alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower    alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl),    —O(alkenyl), chloro, bromo, fluoro, iodo, NO₂, NH₂, —NH(lower    alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂;-   R⁷ and R⁹ are independently hydrogen, OR², hydroxy, alkyl (including    lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl,    —C(O)O(alkyl), —C(O)O(lower alkyl), —O(acyl), —O(lower acyl),    —O(alkyl), —O(lower alkyl), —O(alkenyl), chlorine, bromine, iodine,    NO₂, NH₂, —NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂;-   R¹⁰ is H, alkyl (including lower alkyl), chlorine, bromine, or    iodine; alternatively, R⁷ and R⁹, or R⁷ and R¹⁰ can come together to    form a pi bond; and-   X is O, S, SO₂or CH₂.

In a first preferred subembodiment, a compound of Formula XVII, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H; phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino, or di(loweralkyl)amino; (4)R⁷ and R⁹ are independently hydrogen, OR², alkyl (including loweralkyl), alkenyl, alkynyl, Br-vinyl, O-alkenyl, chlorine, bromine,iodine, NO₂, amino, loweralkylamino or di(loweralkyl)-amino; (5) R¹⁰ isH; and (6) X is O, S, SO₂, or CH₂.

In a second preferred subembodiment, a compound of Formula XVII, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹⁰ isindependently H; phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino or di(loweralkyl)amino; (4) R⁷and R⁹ are independently OR²; (5) R¹⁰ is H, alkyl (including loweralkyl), chlorine, bromine, or iodine; and (6) X is O, S, SO₂ or CH₂.

In a third preferred subembodiment, a compound of Formula XVII, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H; phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino, or di(loweralkyl)amino; (4)R⁷ and R⁹ are independently hydrogen, OR², alkyl (including loweralkyl), alkenyl, alkynyl, Br-vinyl, O-alkenyl, chlorine, bromine,iodine, NO₂, amino, loweralkylamino or di(loweralkyl)-amino; (5) R¹⁰ isH, alkyl (including lower alkyl), chlorine, bromine or iodine; and (6) Xis O.

In a fourth preferred subembodiment, a compound of Formula XVII, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H; phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower. alkyl); sulfonate ester including alkylor arylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino or di(loweralkyl)amino; (4) R⁷and R⁹ are independently OR²; (5) R¹⁰ is H; and (6) X is O, S, SO₂ orCH₂.

In a fifth preferred subembodiment, a compound of Formula XVII, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H; phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino or di(loweralkyl)amino; (4) R⁷and R⁹ are independently OR²; (5) R¹⁰ is H, alkyl (including loweralkyl), chlorine, bromine or iodine; and (6) X is O.

In a sixth preferred subembodiment, a compound of Formula XVII, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H; phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino, or di(loweralkyl)amino; (4)R⁷ and R⁹ are independently hydrogen, OR², alkyl (including loweralkyl), alkenyl, alkynyl, Br-vinyl, O-alkenyl, chlorine, bromine,iodine, NO₂, amino, loweralkylamino, or di(loweralkyl)amino; (5) R¹⁰ isH; and (6) X is O.

In a seventh preferred subembodiment, a compound of Formula XVII, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H; phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino, or di(loweralkyl)amino; (4)R⁷ and R⁹ are independently OR²; (5) R¹⁰ is H; and (6) X is O.

In an eighth preferred subembodiment, a compound of Formula XVII, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently hydrogen, OR², alkyl (including lower alkyl), alkenyl,alkynyl, Br-vinyl, O-alkenyl, chlorine, bromine, iodine, NO₂, amino,loweralkylamino or di(loweralkyl)-amino; (5) R¹⁰ is H, alkyl (includinglower alkyl), chlorine, bromine or iodine; and (6) X is O, S, SO₂, orCH₂.

In a ninth preferred subembodiment, a compound of Formula XVII, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino, or di(loweralkyl)amino; (4)R⁷ and R⁹ are independently OR²; (5) R¹⁰ is H; and (6) X is O, S, SO₂,or CH₂.

In a tenth preferred subembodiment, a compound of Formula XVII, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently OR²; (5) R¹⁰ is H; and (6) X is O, S, SO₂, or CH₂.

In even more preferred subembodiments, a compound of Formula XVII, orits pharmaceutically acceptable salt or prodrug, is provided in which:

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R¹⁰ is hydrogen; and (6) X is O;

(1) Base is guanine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R¹⁰ is hydrogen; and (6) X is O;

(1) Base is cytosine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ andR⁹ are hydroxyl; (5) R¹⁰ is hydrogen; and (6) X is O;

(1) Base is thymine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R¹⁰ is hydrogen; and (6) X is O;

(1) Base is uracil; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R¹⁰ is hydrogen; and (6) X is O;

(1) Base is adenine; (2) R¹ is phosphate; (3) R⁶ is methyl; (4) R⁷ andR⁹ are hydroxyl; (5) R¹⁰ is hydrogen; and (6) X is O;

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is ethyl; (4) R⁷ and R⁹are hydroxyl; (5) R¹⁰ is hydrogen; and (6) X is O;

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is propyl; (4) R⁷ and R⁹are hydroxyl; (5) R¹⁰ is hydrogen; and (6) X is O;

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is butyl; (4) R⁷ and R⁹are hydroxyl; (5) R¹⁰ is hydrogen; and (6) X is O;

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R¹⁰ is hydrogen; and (6) X is S;

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R¹⁰ is hydrogen; and (6) X is SO₂; or

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R¹⁰ is hydrogen; and (6) X is CH₂.

In an twelfth principal embodiment the invention provides a compound ofFormula XVIII, or a pharmaceutically acceptable salt or prodrug thereof:

wherein:

-   Base is a purine or pyrimidine base as defined herein;-   R¹ is independently H; phosphate (including monophosphate,    diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl    (including lower acyl); alkyl (including lower alkyl); sulfonate    ester including alkyl or arylalkyl sulfonyl including    methanesulfonyl and benzyl, wherein the phenyl group is optionally    substituted with one or more substituents as described in the    definition of aryl given herein; a lipid, including a phospholipid;    an amino acid; a carbohydrate; a peptide; a cholesterol; or other    pharmaceutically acceptable leaving group which when administered in    vivo is capable of providing a compound wherein R¹ is independently    H or phosphate;-   R⁶ is hydrogen, hydroxy, alkyl (including lower alkyl), azido,    cyano, alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower    alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl),    —O(alkenyl), chloro, bromo, fluoro, iodo, NO₂, NH₂, —NH(lower    alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂;-   R⁷ and R⁹ are independently hydrogen, OR², alkyl (including lower    alkyl), alkenyl, alkynyl, Br-vinyl, O-alkenyl, chlorine, bromine,    iodine, NO₂, amino, lower alkylamino, or di(loweralkyl)amino;-   R⁸ is H, alkyl (including lower alkyl), chlorine, bromine or iodine;    alternatively, R⁷ and R⁹, or R⁸ and R⁹ can come together to form a    pi bond;-   X is O, S, SO₂or CH₂.

In a first preferred subembodiment, a compound of Formula XVIII, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H; phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently hydrogen, OR², alkyl (including lower alkyl), alkenyl,alkynyl, Br-vinyl, O-alkenyl, chlorine, bromine, iodine, NO₂, amino,loweralkylamino or di(loweralkyl)amino; (5) R⁸ is H, alkyl (includinglower alkyl), chlorine, bromine or iodine; and (6) X is O, S, SO₂ orCH₂.

In a second preferred subembodiment, a compound of Formula XVIII, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H; phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino or di-(loweralkyl)amino; (4)R⁷ and R⁹ are independently OR²; (5) R⁸ is H, alkyl (including loweralkyl), chlorine, bromine, or iodine; and (6) X is O, S, SO₂ or CH₂.

In a third preferred subembodiment, a compound of Formula XVIII, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H; phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino, or di(lower-alkyl)amino; (4)R⁷ and R⁹ are independently hydrogen, OR², alkyl (including loweralkyl), alkenyl, alkynyl, Br-vinyl, O-alkenyl, chlorine, bromine,iodine, NO₂, amino, loweralkylamino, or di(loweralkyl)amino; (5) R⁸ isH; and (6) X is O, S, SO₂ or CH₂.

In a fourth preferred subembodiment, a compound of Formula XVIII, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H; phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino, or di(loweralkyl)amino; (4)R⁷ and R⁹ are independently hydrogen, OR², alkyl (including loweralkyl), alkenyl, alkynyl, Br-vinyl, O-alkenyl, chlorine, bromine,iodine, NO₂, amino, loweralkylamino, or di(loweralkyl)amino; (5) R⁸ isH, alkyl (including lower alkyl), chlorine, bromine, or iodine; and (6)X is O.

In a fifth preferred subembodiment, a compound of Formula XVIII, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H; phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino, or di(loweralkyl)amino; (4)R⁷ and R⁹ are independently OR²; (5) R⁸ is H; and (6) X is O, S, SO₂, orCH₂.

In a sixth preferred subembodiment, a compound of Formula XVIII, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H; phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino, or di(loweralkyl)am no; (4)R⁷ and R⁹ are independently OR²; (5) R⁸ is H, alkyl (including loweralkyl), chlorine, bromine, or iodine; and (6) X is O.

In a seventh preferred subembodiment, a compound of Formula XVIII, orits pharmaceutically acceptable salt or prodrug is provided in which:(1) Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H; phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino, or di(loweralkyl)amino; (4)R⁷ and R⁹ are independently hydrogen, OR², alkyl (including loweralkyl), alkenyl, alkynyl, Br-vinyl, O-alkenyl, chlorine, bromine,iodine, NO₂, amino, loweralkylamino, or di(loweralkyl)amino; (5) R⁸ isH; and (6) X is O.

In an eighth preferred subembodiment, a compound of Formula XVIII, orits pharmaceutically acceptable salt or prodrug, is provided in which:(1) Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino or di(loweralkyl)amino; (4) R⁷and R⁹ are independently OR²; (5) R⁸ is H; and (6) X is O, S, SO₂ orCH₂.

In a ninth preferred subembodiment, a compound of Formula XVIII, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently OR²; (5) R is H; and (6) X is O, S, SO₂, or CH₂.

In a tenth preferred subembodiment, a compound of Formula XVIII, or itspharmaceutically acceptable salt or prodrug, is provided in which: (1)Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently OR²; (5) R⁸ is H; and (6) X is O.

In even more preferred subembodiments, a compound of Formula XVIII, orits pharmaceutically acceptable salt or prodrug, is provided in which:

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ is hydrogen; and (6) X is O;

(1) Base is guanine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ is hydrogen; and (6) X is O;

(1) Base is cytosine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ andR⁹ are hydroxyl; (5) R⁸ is hydrogen; and (6) X is O;

(1) Base is thymine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ is hydrogen; and (6) X is O;

(1) Base is uracil; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ is hydrogen; and (6) X is O;

(1) Base is adenine; (2) R¹ is phosphate; (3) R⁶ is methyl; (4) R⁷ andR⁹ are hydroxyl; (5) R⁸ is hydrogen; and (6) X is O;

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is ethyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ is hydrogen; and (6) X is O;

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is propyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸is hydrogen; and (6) X is O;

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is butyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ is hydrogen; and (6) X is O;

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ is hydrogen; and (6) X is S;

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ is hydrogen; and (6) X is SO₂; or

(1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷ and R⁹are hydroxyl; (5) R⁸ is hydrogen; and (6) X is CH₂.

The β-D- and β-L-nucleosides of this invention may inhibit HCVpolymerase activity. Nucleosides can be screened for their ability toinhibit HCV polymerase activity in vitro according to screening methodsset forth more particularly herein. One can readily determine thespectrum of activity by evaluating the compound in the assays describedherein or with another confirmatory assay.

In one embodiment the efficacy of the anti-HCV compound is measuredaccording to the concentration of compound necessary to reduce theplaque number of the virus in vitro, according to methods set forth moreparticularly herein, by 50% (i.e. the compound's EC₅₀). In preferredembodiments the compound exhibits an EC₅₀ of less than 15 or 10micromolar, when measured according to the polymerase assay described inFerrari et al., Jnl. of Vir., 73:1649-1654, 1999; Ishii et al.,Hepatology, 29:1227-1235,1999; Lohmann et al., Jnl. of Bio. Chem.,274:10807-10815, 1999; or Yamashita et al, Jnl. of Bio. Chem.,273:15479-15486, 1998.

The active compound can be administered as any salt or prodrug that uponadministration to the recipient is capable of providing directly orindirectly the parent compound, or that exhibits activity itself.Nonlimiting examples are the pharmaceutically acceptable salts(alternatively referred to as “physiologically acceptable salts”), and acompound that has been alkylated or acylated at the 5′-position or onthe purine or pyrimidine base (a type of “pharmaceutically acceptableprodrug”). Further, the modifications can affect the biological activityof the compound, in some cases increasing the activity over the parentcompound. This can easily be assessed by preparing the salt or prodrugand testing its antiviral activity according to the methods describedherein, or other methods known to those skilled in the art.

II. Definitions

The term alkyl, as used herein, unless otherwise specified, refers to asaturated straight, branched, or cyclic, primary, secondary, or tertiaryhydrocarbon of typically C₁ to C₁₀, and specifically includes methyl,ethyl, propyl, isopropyl, cyclopropyl, butyl, isobutyl, t-butyl, pentyl,cyclopentyl, isopentyl, neopentyl, hexyl, isohexyl, cyclohexyl,cyclohexylmethyl, 3-methylpentyl, 2,2-dimethylbutyl, and2,3-dimethylbutyl. The term includes both substituted and unsubstitutedalkyl groups. Moieties with which the alkyl group can be substituted areselected from the group consisting of hydroxyl, amino, alkylamino,arylamino, alkoxy, aryloxy, nitro, cyano, sulfonic acid, sulfate,phosphonic acid, phosphate, or phosphonate, either unprotected, orprotected as necessary, as known to those skilled in the art, forexample, as taught in Greene, et al., Protective Groups in OrganicSynthesis, John Wiley and Sons, Second Edition, 1991, herebyincorporated by reference.

The term lower alkyl, as used herein, and unless otherwise specified,refers to a C₁ to C₄ saturated straight, branched, or if appropriate, acyclic (for example, cyclopropyl) alkyl group, including bothsubstituted and unsubstituted forms. Unless otherwise specificallystated in this application, when alkyl is a suitable moiety, lower alkylis preferred. Similarly, when alkyl or lower alkyl is a suitable moiety,unsubstituted alkyl or lower alkyl is preferred.

The term alkylamino or arylamino refers to an amino group that has oneor two alkyl or aryl substituents, respectively.

The term “protected” as used herein and unless otherwise defined refersto a group that is added to an oxygen, nitrogen, or phosphorus atom toprevent its further reaction or for other purposes. A wide variety ofoxygen and nitrogen protecting groups are known to those skilled in theart of organic synthesis.

The term aryl, as used herein, and unless otherwise specified, refers tophenyl, biphenyl, or naphthyl, and preferably phenyl. The term includesboth substituted and unsubstituted moieties. The aryl group can besubstituted with one or more moieties selected from the group consistingof hydroxyl, amino, alkylamino, arylamino, alkoxy, aryloxy, nitro,cyano, sulfonic acid, sulfate, phosphonic acid, phosphate, orphosphonate, either unprotected, or protected as necessary, as known tothose skilled in the art, for example, as taught in Greene, et al.,Protective Groups in Organic Synthesis, John Wiley and Sons, SecondEdition, 1991.

The term alkaryl or alkylaryl refers to an alkyl group with an arylsubstituent. The term aralkyl or arylalkyl refers to an aryl group withan alkyl substituent.

The term halo, as used herein, includes chloro, bromo, iodo, and fluoro.

The term purine or pyrimidine base includes, but is not limited to,adenine, N⁶-alkylpurines, N⁶-acylpurines (wherein acyl is C(O)(alkyl,aryl, alkylaryl, or arylalkyl), N⁶-benzylpurine, N⁶-halopurine,N⁶-vinylpurine, N⁶-acetylenic purine, N⁶-acyl purine, N⁶-hydroxyalkylpurine, N⁶-thioalkyl purine, N²-alkylpurines, N²-alkyl-6-thiopurines,thymine, cytosine, 5-fluorocytosine, 5-methylcytosine, 6-azapyrimidine,including 6-azacytosine, 2- and/or 4-mercaptopyrmidine, uracil,5-halouracil, including 5-fluorouracil, C⁵-alkylpyrimidines,C⁵-benzylpyrimidines, C⁵-halopyrimidines, C⁵-vinylpyrimidine,C⁵-acetylenic pyrimidine, C⁵-acyl pyrimidine, C⁵-hydroxyalkyl purine,C⁵-amidopyrimidine, C⁵-cyanopyrimidine, C⁵-nitropyrimidine,C⁵-aminopyrimidine, N²-alcylpurines, N²-alkyl-6-thiopurines,5-azacytidinyl, 5-azauracilyl, triazolopyridinyl, imidazolopyridinyl,pyrrolopyrimidinyl, and pyrazolopyrimidinyl. Purine bases include, butare not limited to, guanine, adenine, hypoxanthine, 2,6-diaminopurine,and 6-chloropurine. Functional oxygen and nitrogen groups on the basecan be protected as necessary or desired. Suitable protecting groups arewell known to those skilled in the art, and include trimethylsilyl,dimethylhexylsilyl, t-butyldimethylsilyl, and t-butyldiphenylsilyl,trityl, alkyl groups, and acyl groups such as acetyl and propionyl,methanesulfonyl, and p-toluenesulfonyl.

The term acyl refers to a carboxylic acid ester in which thenon-carbonyl moiety of the ester group is selected from straight,branched, or cyclic alkyl or lower alkyl, alkoxyalkyl includingmethoxymethyl, aralkyl including benzyl, aryloxyalkyl such asphenoxymethyl, aryl including phenyl optionally substituted with chloro,bromo, fluoro, iodo, C₁ to C₄ alkyl or C₁ to C₄ alkoxy, sulfonate esterssuch as alkyl or aralkyl sulphonyl including methanesulfonyl, the mono,di or triphosphate ester, trityl or monomethoxytrityl, substitutedbenzyl, trialkylsilyl (e.g. dimethyl-t-butylsilyl) ordiphenylmethylsilyl. Aryl groups in the esters optimally comprise aphenyl group. The term “lower acyl” refers to an acyl group in which thenon-carbonyl moiety is a lower alkyl.

As used herein, the term “substantially free of” or “substantially inthe absence of” refers to a nucleoside composition that includes atleast 85 or 90% by weight, preferably 95% to 98% by weight, and evenmore preferably 99% to 100% by weight, of the designated enantiomer ofthat nucleoside. In a preferred embodiment, in the methods and compoundsof this invention, the compounds are substantially free of enantiomers.

Similarly, the term “isolated” refers to a nucleoside composition thatincludes at least 85 or 90% by weight, preferably 95% to 98% by weight,and even more preferably 99% to 100% by weight, of the nucleoside, theremainder comprising other chemical species or enantiomers.

The term “independently” is used herein to indicate that the variablewhich is independently applied varies independently from application toapplication. Thus, in a compound such as R″XYR″, wherein R″ is“independently carbon or nitrogen,” both R″ can be carbon, both R″ canbe nitrogen, or one R″ can be carbon and the other R″ nitrogen.

The term host, as used herein, refers to an unicellular or multicellularorganism in which the virus can replicate, including cell lines andanimals, and preferably a human. Alternatively, the host can be carryinga part of the hepatitis C viral genome, whose replication or functioncan be altered by the compounds of the present invention. The term hostspecifically refers to infected cells, cells transfected with all orpart of the HCV genome and animals, in particular, primates (includingchimpanzees) and humans. In most animal applications of the presentinvention, the host is a human patient. Veterinary applications, incertain indications, however, are clearly anticipated by the presentinvention (such as chimpanzees).

The term “pharmaceutically acceptable salt or prodrug” is usedthroughout the specification to describe any pharmaceutically acceptableform (such as an ester, phosphate ester, salt of an ester or a relatedgroup) of a nucleoside compound which, upon administration to a patient,provides the nucleoside compound. Pharmaceutically acceptable saltsinclude those derived from pharmaceutically acceptable inorganic ororganic bases and acids. Suitable salts include those derived fromalkali metals such as potassium and sodium, alkaline earth. metals suchas calcium and magnesium, among numerous other acids well known in thepharmaceutical art. Pharmaceutically acceptable prodrugs refer to acompound that is metabolized, for example hydrolyzed or oxidized, in thehost to form the compound of the present invention. Typical examples ofprodrugs include compounds that have biologically labile protectinggroups on a functional moiety of the active compound. Prodrugs includecompounds that can be oxidized, reduced, aminated, deaminated,hydroxylated, dehydroxylated, hydrolyzed, dehydrolyzed, alkylated,dealkylated, acylated, deacylated, phosphorylated, dephosphorylated toproduce the active compound. The compounds of this invention possessantiviral activity against HCV, or are metabolized to a compound thatexhibits such activity.

III. Nucleotide Salt or Prodrug Formulations

In cases where compounds are sufficiently basic or acidic to form stablenontoxic acid or base salts, administration of the compound as apharmaceutically acceptable salt may be appropriate. Examples ofpharmaceutically acceptable salts are organic acid addition salts formedwith acids, which form a physiological acceptable anion, for example,tosylate, methanesulfonate, acetate, citrate, malonate, tartarate,succinate, benzoate, ascorbate, α-ketoglutarate, and α-glycerophosphate.Suitable inorganic salts may also be formed, including, sulfate,nitrate, bicarbonate, and carbonate salts.

Pharmaceutically acceptable salts may be obtained using standardprocedures well known in the art, for example by reacting a sufficientlybasic compound such as an amine with a suitable acid affording aphysiologically acceptable anion. Alkali metal (for example, sodium,potassium or lithium) or alkaline earth metal (for example calcium)salts of carboxylic acids can also be made.

Any of the nucleosides described herein can be administered as anucleotide prodrug to increase the activity, bioavailability, stabilityor otherwise alter the properties of the nucleoside. A number ofnucleotide prodrug ligands are known. In general, alkylation, acylationor other lipophilic modification of the mono, di or triphosphate of thenucleoside will increase the stability of the nucleotide. Examples ofsubstituent groups that can replace one or more hydrogens on thephosphate moiety are alkyl, aryl, steroids, carbohydrates, includingsugars, 1,2-diacylglycerol and alcohols. Many are described in R. Jonesand N. Bischofberger, Antiviral Research, 27 (1995) 1-17. Any of thesecan be used in combination with the disclosed nucleosides to achieve adesired effect.

The active nucleoside can also be provided as a 5′-phosphoether lipid ora 5′-ether lipid, as disclosed in the following references, which areincorporated by reference herein: Kucera, L. S., N. Iyer, E. Leake, A.Raben, Modest E. K., D. L. W., and C. Piantadosi. 1990. “Novelmembrane-interactive ether lipid analogs that inhibit infectious HIV-1production and induce defective virus formation.” AIDS Res. Hum. RetroViruses. 6:491-501; Piantadosi, C., J. Marasco C. J., S. L.Morris-Natschke, K. L. Meyer, F. Gumus, J. R. Surles, K. S. Ishaq, L. S.Kucera, N. Iyer, C. A. Wallen, S. Piantadosi, and E. J. Modest. 1991.“Synthesis and evaluation of novel ether lipid nucleoside conjugates foranti-HIV activity.” J. Med. Chem. 34:1408.1414; Hosteller, K. Y., D. D.Richman, D. A. Carson, L. M. Stuhmiller, G. M. T. van Wijk, and H. vanden Bosch. 1992. “Greatly enhanced inhibition of human immunodeficiencyvirus type 1 replication in CEM and HT4-6C cells by 3′-deoxythymidinediphosphate dimyristoylglycerol, a lipid prodrug of 3, -deoxythymidine.”Antimicrob. Agents Chemother. 36:2025.2029; Hosetler, K. Y., L. M.Stuhmiller, H. B. Lenting, H. van den Bosch, and D. D. Richman, 1990.“Synthesis and antiretroviral activity of phospholipid analogs ofazidothymidine and other antiviral nucleosides.” J. Biol. Chem.265:61127.

Nonlimiting examples of U.S. patents that disclose suitable lipophilicsubstituents that can be covalently incorporated into the nucleoside,preferably at the 5′-OH position of the nucleoside or lipophilicpreparations, include U.S. Pat. No. 5,149,794 (Sep. 22, 1992, Yatvin etal.); U.S. Pat. No. 5,194,654 (Mar. 16, 1993, Hostetler et al., U.S.Pat. No. 5,223,263 (Jun. 29, 1993, Hostetler et al.); U.S. Pat. No.5,256,641 (Oct. 26, 1993, Yatvin et al.); U.S. Pat. No. 5,411,947 (May2, 1995, Hostetler et al.); U.S. Pat. No. 5,463,092 (Oct. 31, 1995,Hostetler et al.); U.S. Pat. No. 5,543,389 (Aug. 6, 1996, Yatvin etal.); U.S. Pat. No. 5,543,390 (Aug. 6, 1996, Yatvin et al.); U.S. Pat.No. 5,543,391 (Aug. 6, 1996, Yatvin et al.); and U.S. Pat. No. 5,554,728(Sep. 10, 1996; Basava et al.), all of which are incorporated herein byreference. Foreign patent applications that disclose lipophilicsubstituents that can be attached to the nucleosides of the presentinvention, or lipophilic preparations, include WO 89/02733, WO 90/00555,WO 91/16920, WO 91/18914, WO 93/00910, WO 94/26273, WO 96/15132, EP 0350 287, EP 93917054.4, and WO 91/19721.

IV. Combination and Alternation Therapy

It has been recognized that drug-resistant variants of HCV can emergeafter prolonged treatment with an antiviral agent. Drug resistance mosttypically occurs by mutation of a gene that encodes for an enzyme usedin viral replication. The efficacy of a drug against HCV infection canbe prolonged, augmented, or restored by administering the compound incombination or alternation with a second, and perhaps third, antiviralcompound that induces a different mutation from that caused by theprinciple drug. Alternatively, the pharmacokinetics, biodistribution orother parameter of the drug can be altered by such combination oralternation therapy. In general, combination therapy is typicallypreferred over alternation therapy because it induces multiplesimultaneous stresses on the virus.

Nonlimiting examples of antiviral agents that can be used in combinationwith the compounds disclosed herein include:

(1) an interferon and/or ribavirin (Battaglia, A. M. et al., Ann.Pharmacother. 34:487-494, 2000); Berenguer, M. et al. Antivir. Ther.3(Suppl. 3):125-136, 1998);

(2) Substrate-based NS3 protease inhibitors (Attwood et al., Antiviralpeptide derivatives, PCT WO 98/22496, 1998; Attwood et al., AntiviralChemistry and Chemotherapy 10.259-273, 1999; Attwood et al., Preparationand use of amino acid derivatives as anti-viral agents, German PatentPublication DE 19914474; Tung et al. Inhibitors of serine proteases,particularly hepatitis C virus NS3 protease, PCT WO 98/17679), includingalphaketoamides and hydrazinoureas, and inhibitors that terminate in anelectrophile such as a boronic acid or phosphonate. Llinas-Brunet et al,Hepatitis C inhibitor peptide analogues, PCT WO 99/07734.

(3) Non-substrate-based inhibitors such as2,4,6-trihydroxy-3-nitro-benzamide derivatives (Sudo K. et al.,Biochemical and Biophysical Research Communications, 238:643-647, 1997;Sudo K. et al. Antiviral Chemistry and Chemotherapy 9:186, 1998),including RD3-4082 and RD3-4078, the former substituted on the amidewith a 14 carbon chain and the latter processing a para-phenoxyphenylgroup;

(4) Thiazolidine derivatives which show relevant inhibition in areverse-phase HPLC assay with an NS3/4A fusion protein and NS5A/5Bsubstrate (Sudo K. et al., Antiviral Research 32:9-18, 1996), especiallycompound RD-1-6250, possessing a fused cinnamoyl moiety substituted witha long alkyl chain, RD4 6205 and RD4 6193;

(5) Thiazolidines and benzanilides identified in Kakiuchi N. et al. J.EBS Letters 421:217-220; Takeshita N. et al. Analytical Biochemistry247:242-246, 1997;

(6) A phenan-threnequmnone possessing activity against HCV protease in aSDS-PAGE and autoradiography assay isolated from the fermentationculture broth of Streptomyces sp., Sch 68631 (Chu M. et al., TetrahedronLetters 37:7229-7232, 1996), and Sch 351633, isolated from the fungusPenicillium griscofuluum, which demonstrates activity in a scintillationproximity assay (Chu M. et al., Bioorganic and Medicinal ChemistryLetters 9:1949-1952);

(7) Selective NS3 inhibitors based on the macromolecule elgin c,isolated from leech (Qasim M. A. et al., Biochemistry 36:1598-1607,1997);

(8) HCV helicase inhibitors (Diana G. D. et al., Compounds, compositionsand methods for treatment of hepatitis C, U.S. Pat. No. 5,633,358; DianaG. D. et al., Piperidine derivatives, pharmaceutical compositionsthereof and their use in the treatment of hepatitis C, PCT WO 97/36554);

(9) HCV polymerase inhibitors such as nucleotide analogues, gliotoxin(Ferrari R. et al. Journal of Virology 73:1649-1654, 1999), and thenatural product cerulenin (Lohmann. V. et al., Virology 249:108-118,1998);

(10) Antisense phosphorothioate oligodeoxynucleotides (S-ODN)complementary to sequence stretches in the 5′non-coding region (NCR) ofthe HCV (Alt M. et al., Hepatology 22:707-717, 1995), or nucleotides326-348 comprising the 3′ end of the NCR and nucleotides 371-388 locatedin the core coding region of the IICV RNA (Alt M. et al., Archives ofVirology 142:589-599, 1997; Galderisi U. et al., Journal of CellularPhysiology 181:251-257, 1999);

(11) Inhibitors of IRES-dependent translation (Ikeda N et al., Agent forthe prevention and treatment of hepatitis C, Japanese Patent PublicationJP-08268890; Kai Y. et al. Prevention and treatment of viral diseases,Japanese Patent Publication JP-10101591);

(12) Nuclease-resistant ribozymes. (Maccjak D. J. et al., Hepatology 30abstract 995, 1999); and

(13) Other miscellaneous compounds including 1-amino-alkylcyclohexanes(U.S. Pat. No. 6,034,134 to Gold et al.), alkyl lipids (U.S. Pat. No.5,922,757 to Chojkier et al.), vitamin E and other antioxidants (U.S.Pat. No. 5,922,757 to Chojkier et al.), squalene, amantadine, bile acids(U.S. Pat. No. 5,846,964 to Ozeki et al.),N-(phosphonoacetyl)-L-aspartic acid, (U.S. Pat. No. 5,830,905 to Dianaet al.), benzenedicarboxamides (U.S. Pat. No. 5,633,388 to Diana etal.), polyadenylic acid derivatives (U.S. Pat. No. 5,496,546 to Wang etal.), 2′,3′-dideoxyinosine (U.S. Pat. No. 5,026,687 to Yarchoan et al.),and benzimidazoles (U.S. Pat. No. 5,891,874 to Colacino et al.).

V. Pharmaceutical Compositions

Hosts, including humans, infected with HCV, or a gene fragment thereof,can be treated by administering to the patient an effective amount ofthe active compound or a pharmaceutically acceptable prodrug or saltthereof in the presence of a pharmaceutically acceptable carrier ordiluent. The active materials can be administered by any appropriateroute, for example, orally, parenterally, intravenously, intradermally,subcutaneously, or topically, in liquid or solid form.

A preferred dose of the compound for HCV will be in the range from about1 to 50 mg/kg, preferably 1 to 20 mg/kg, of body weight per day, moregenerally 0.1 to about 100 mg per kilogram body weight of the recipientper day. The effective dosage range of the pharmaceutically acceptablesalts and prodrugs can be calculated based on the weight of the parentnucleoside to be delivered. If the salt or prodrug exhibits activity initself, the effective dosage can be estimated as above using the weightof the salt or prodrug, or by other means known to those skilled in theart.

The compound is conveniently administered in unit any suitable dosageform, including but not limited to one containing 7 to 3000 mg,preferably 70 to 1400 mg of active ingredient per unit dosage form. Aoral dosage of 50-1000 mg is usually convenient.

Ideally the active ingredient should be administered to achieve peakplasma concentrations of the active compound of from about 0.2 to 70 μM,preferably about 1.0 to 10 μM. This may be achieved, for example, by theintravenous injection of a 0.1 to 5% solution of the active ingredient,optionally in saline, or administered as a bolus of the activeingredient.

The concentration of active compound in the drug composition will dependon absorption, inactivation and excretion rates of the drug as well asother factors known to those of skill in the art. It is to be noted thatdosage values will also vary with the severity of the condition to bealleviated. It is to be further understood that for any particularsubject, specific dosage regimens should be adjusted over time accordingto the individual need and the professional judgment of the personadministering or supervising the administration of the compositions, andthat the concentration ranges set forth herein are exemplary only andare not intended to limit the scope or practice of the claimedcomposition. The active ingredient may be administered at once, or maybe divided into a number of smaller doses to be administered at varyingintervals of time.

A preferred mode of administration of the active compound is oral. Oralcompositions will generally include an inert diluent or an ediblecarrier. They may be enclosed in gelatin capsules or compressed intotablets. For the purpose of oral therapeutic administration, the activecompound can be incorporated with excipients and used in the form oftablets, troches, or capsules. Pharmaceutically compatible bindingagents, and/or adjuvant materials can be included as part of thecomposition.

The tablets, pills, capsules, troches and the like can contain any ofthe following ingredients, or compounds of a similar nature: a bindersuch as microcrystalline cellulose, gum tragacanth or gelatin; anexcipient such as starch or lactose, a disintegrating agent such asalginic acid, Primogel, or corn starch; a lubricant such as magnesiumstearate or Sterotes; a glidant such as colloidal silicon dioxide; asweetening agent such as sucrose or saccharin; or a flavoring agent suchas peppermint, methyl salicylate, or orange flavoring. When the dosageunit form is a capsule, it can contain, in addition to material of theabove type, a liquid carrier such as a fatty oil. In addition, dosageunit forms can contain various other materials which modify the physicalform of the dosage unit, for example, coatings of sugar, shellac, orother enteric agents.

The compound can be administered as a component of an elixir,suspension, syrup, wafer, chewing gum or the like. A syrup may contain,in addition to the active compounds, sucrose as a sweetening agent andcertain preservatives, dyes and colorings and flavors.

The compound or a pharmaceutically acceptable prodrug or salts thereofcan also be mixed with other active materials that do not impair thedesired action, or with materials that supplement the desired action,such as antibiotics, antifungals, anti-inflammatories, or otherantivirals, including other nucleoside. compounds. Solutions orsuspensions used for parenteral, intradermal, subcutaneous, or topicalapplication can include the following components: a sterile diluent suchas water for injection, saline solution, fixed oils, polyethyleneglycols, glycerine, propylene glycol or other synthetic solvents;antibacterial agents such as benzyl alcohol or methyl parabens;antioxidants such as ascorbic acid or sodium bisulfite; chelating agentssuch as ethylenediaminetetraacetic acid; buffers such as acetates,citrates or phosphates and agents for the adjustment of tonicity such assodium chloride or dextrose. The parental preparation can be enclosed inampoules, disposable syringes or multiple dose vials made of glass orplastic.

If administered intravenously, preferred carriers are physiologicalsaline or phosphate buffered saline (PBS).

In a preferred embodiment, the active compounds are prepared withcarriers that will protect the compound against rapid elimination fromthe body, such as a controlled release formulation, including implantsand microencapsulated delivery systems. Biodegradable, biocompatiblepolymers can be used, such as ethylene vinyl acetate, polyanhydrides,polyglycolic acid, collagen, polyorthoesters and polylactic acid.Methods for preparation of such formulations will be apparent to thoseskilled in the art. The materials can also be obtained commercially fromAlza Corporation.

Liposomal suspensions (including liposomes targeted to infected cellswith monoclonal antibodies to viral antigens) are also preferred aspharmaceutically acceptable carriers. These may be prepared according tomethods known to those skilled in the art, for example, as described inU.S. Pat. No. 4,522,811 (which is incorporated herein by reference inits entirety). For example, liposome formulations may be prepared bydissolving appropriate lipid(s) (such as stearoyl phosphatidylethanolamine, stearoyl phosphatidyl choline, arachadoyl phosphatidylcholine, and cholesterol) in an inorganic solvent that is thenevaporated, leaving behind a thin film of dried lipid on the surface ofthe container. An aqueous solution of the active compound or itsmonophosphate, diphosphate, and/or triphosphate derivatives is thenintroduced into the container. The container is then swirled by hand tofree lipid material from the sides of the container and to disperselipid aggregates, thereby forming the liposomal suspension.

VI. Processes for the Preparation of Active Compounds

The nucleosides of the present invention can be synthesized by any meansknown in the art. In particular, the synthesis of the presentnucleosides can be achieved by either alkylating the appropriatelymodified sugar, followed by glycosylation or glycosylation followed byalkylation of the nucleoside. The following non-limiting embodimentsillustrate some general methodology to obtain the nucleosides of thepresent invention.

A. General Synthesis of 1′-C-Branched Nucleosides

1 ′-C-Branched ribonucleosides of the following structure:

wherein BASE is a purine or pyrimidine base as defined herein;

-   R⁷ and R⁹ are independently hydrogen, OR², hydroxy, alkyl (including    lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl,    —C(O)O(alkyl), —C(O)O(lower alkyl), —O(acyl), —O(lower acyl),    —O(alkyl), —O(lower alkyl), —O(alkenyl), chlorine, bromine, iodine,    NO₂, NH₂, —NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂;-   R⁸ and R¹⁰ are independently H, alkyl (including lower alkyl),    chlorine, bromine or iodine;-   alternatively, R⁷ and R⁹, R⁷ and R¹⁰, R⁸ and R⁹, or R⁸ and R¹⁰ can    come together to form a pi bond;-   R¹ and R² are independently H; phosphate (including monophosphate,    diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl    (including lower acyl); alkyl (including lower alkyl); sulfonate    ester including alkyl or arylalkyl sulfonyl including    methanesulfonyl and benzyl, wherein the phenyl group is optionally    substituted with one or more substituents as described in the    definition of aryl given herein; a lipid, including a phospholipid;    an amino acid; a carbohydrate; a peptide; a cholesterol; or other    pharmaceutically acceptable leaving group which when administered in    vivo is capable of providing a compound wherein R¹ or R² is    independently H or phosphate;-   R⁶ is an alkyl, chloro-, bromo-, fluoro-, or iodo-alkyl (i.e. CF₃),    alkenyl, or alkynyl (i.e. allyl); and-   X is O, S, SO₂ or CH₂    can be prepared by one of the following general methods.    1) Modification from the Lactone

The key starting material for this process is an appropriatelysubstituted lactone. The lactone can be purchased or can be prepared byany known means including standard epimerization, substitution andcyclization techniques. The lactone can be optionally protected with asuitable protecting group, preferably with an acyl or silyl group, bymethods well known to those skilled in the art, as taught by Greene etal. Protective Groups in Organic Synthesis, John Wiley and Sons, SecondEdition, 1991. The protected lactone can then be coupled with a suitablecoupling agent, such as an organometallic carbon nucleophile, such as aGrignard reagent, an organolithium, lithium dialkyl copper or R⁶—SiMe₃in TBAF with the appropriate non-protic solvent at a suitabletemperature, to give the 1′-alkylated sugar.

The optionally activated sugar can then be coupled to the BASE bymethods well known to those skilled in the art, as taught by TownsendChemistry of Nucleosides and Nucleotides, Plenum Press, 1994. Forexample, an acylated sugar can be coupled to a silylated base with alewis acid, such as tin tetrachloride, titanium tetrachloride ortrimethylsilyltriflate in the appropriate solvent at a suitabletemperature.

Subsequently, the nucleoside can be deprotected by methods well known tothose skilled in the art, as taught by Greene et al. Protective Groupsin Organic Synthesis, John Wiley and Sons, Second Edition, 1991.

In a particular embodiment, the 1′-C-branched ribonucleoside is desired.The synthesis of a ribonucleoside is shown in Scheme 1. Alternatively,deoxyribo-nucleoside is desired. To obtain these nucleosides, the formedribonucleoside can optionally be protected by methods well known tothose skilled in the art, as taught by Greene et al. Protective Groupsin Organic Synthesis, John Wiley and Sons, Second Edition, 1991, andthen the 2′-OH can be reduced with a suitable reducing agent.Optionally, the 2′-hydroxyl can be activated to facilitate reduction;i.e. via the Barton reduction.

2. Alternative Method for the Preparation of 1′C-Branched Nucleosides

The key starting material for this process is an appropriatelysubstituted hexose. The hexose can be purchased or can be prepared byany known means including standard epimerization, such as alkalinetreatment, substitution and coupling techniques. The hexose can beselectively protected to give the appropriate hexa-furanose, as taughtby Townsend Chemistry of Nucleosides and Nucleotides, Plenum Press,1994.

The 1′-hydroxyl can be optionally activated to a suitable leaving groupsuch as an acyl group or a chloro, bromo, fluoro, iodo via acylation orhalogenation, respectively. The optionally activated sugar can then becoupled to the BASE by methods well known to those skilled in the art,as taught by Townsend Chemistry of Nucleosides and Nucleotides, PlenumPress, 1994. For example, an acylated sugar can be coupled to asilylated base with a lewis acid, such as tin tetrachloride, titaniumtetrachloride or trimethylsilyltriflate in the appropriate solvent at asuitable temperature. Alternatively, a halo-sugar can be coupled to asilylated base with the presence of trimethylsilyltriflate.

The 1′-CH₂—OH, if protected, can be selectively deprotected by methodswell known in the art. The resultant primary hydroxyl can befunctionalized to yield various C-branched nucleosides. For example, theprimary hydroxyl can be reduced to give the methyl, using a suitablereducing agent. Alternatively, the hydroxyl can be activated prior toreduction to facilitate the reaction; i.e. via the Barton reduction. Inan alternate embodiment, the primary hydroxyl can be oxidized to thealdehyde, then coupled with a carbon nucleophile, such as a Grignardreagent, an organolithium, lithium dialkylcopper or R⁶—SiMe₃ in TBAFwith the appropriate non-protic solvent at a suitable temperature.

In a particular embodiment, the 1′-C-branched ribonucleoside is desired.The synthesis of a ribonucleoside is shown in Scheme 2. Alternatively,deoxyribo-nucleoside is desired. To obtain these nucleosides, the formedribonucleoside can optionally be protected by methods well known tothose skilled in the art, as taught by Greene et al. Protective Groupsin Organic Synthesis, John Wiley and Sons, Second Edition, 1991, andthen the 2′-OH can be reduced with a suitable reducing agent.Optionally, the 2′-hydroxyl can be activated to facilitate reduction;i.e. via the Barton reduction.

In addition, the L-enantiomers corresponding to the compounds of theinvention can be prepared following the same general methods (1 or 2),beginning with the corresponding L-sugar or nucleoside L-enantiomer asstarting material.

B. General Synthesis of 2′-C-Branched Nucleosides

2′-C-Branched ribonucleosides of the following structure:

wherein BASE is a purine or pyrimidine base as defined herein;

-   R⁷ and R⁹ are independently hydrogen, OR², hydroxy, alkyl (including    lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl,    —C(O)O(alkyl), —C(O)O(lower alkyl), —O(acyl), —O(lower acyl),    —O(alkyl), —O(lower alkyl), —O(alkenyl), chlorine, bromine, iodine,    NO₂, NH₂, —NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂;-   R¹⁰ is H, alkyl (including lower alkyl), chlorine, bromine or    iodine;-   alternatively, R⁷ and R⁹, or R⁷ and R¹⁰ can come together to form a    pi bond;-   R¹ and R² are independently H; phosphate (including monophosphate,    diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl    (including lower acyl); alkyl (including lower alkyl); sulfonate    ester including alkyl or arylalkyl sulfonyl including    methanesulfonyl and benzyl, wherein the phenyl group is optionally    substituted with one or more substituents as described in the    definition of aryl given herein; a lipid, including a phospholipid;    an amino acid; a carbohydrate; a peptide; a cholesterol; or other    pharmaceutically acceptable leaving group which when administered in    vivo is capable of providing a compound wherein R¹ or R² is    independently H or phosphate;-   R⁶ is an alkyl, chloro-, bromo-, fluoro-, iodo-alkyl (i.e. CF₃),    alkenyl, or alkynyl (i.e. allyl); and-   X is O, S, SO₂ or CH₂    can be prepared by one of the following general methods.    1. Glycosylation of the Nucleobase with an Appropriately Modified    Sugar

The key starting material for this process is an appropriatelysubstituted sugar with a 2′-OH and 2′-H, with the appropriate leavinggroup (LG), for example an acyl group or a chloro, bromo, fluoro oriodo. The sugar can be purchased or can be prepared by any known meansincluding standard epimerization, substitution, oxidation and reductiontechniques. The substituted sugar can then be oxidized with theappropriate oxidizing agent in a compatible solvent at a suitabletemperature to yield the 2′-modified sugar. Possible oxidizing agentsare Jones reagent (a mixture of chromic acid and sulfuric acid),Collins's reagent (dipyridine Cr(VI) oxide, Corey's reagent (pyridiniumchlorochromate), pyridinium dichromate, acid dichromate, potassiumpermanganate, MnO₂, ruthenium tetroxide, phase transfer catalysts suchas chromic acid or permanganate supported on a polymer, Cl₂-pyridine,H₂O₂-ammonium molybdate, NaBrO₂—CAN, NaOCl in HOAc, copper chromite,copper oxide, Raney nickel, palladium acetate, Meerwin-Pondorf-Verleyreagent (aluminum t-butoxide with another ketone) andN-bromosuccinimide.

Then coupling of an organometallic carbon nucleophile, such as aGrignard reagent, an organolithium, lithium dialkylcopper or R⁶—SiMe₃ inTBAF with the ketone with the appropriate non-protic solvent at asuitable temperature, yields the 2′-alkylated sugar. The alkylated sugarcan be optionally protected with a suitable protecting group, preferablywith an acyl or silyl group, by methods well known to those skilled inthe art, as. taught by Greene et al. Protective Groups in OrganicSynthesis, John Wiley and Sons, Second Edition, 1991.

The optionally protected sugar can then be coupled to the BASE bymethods well known to those skilled in the art, as taught by TownsendChemistry of Nucleosides and Nucleotides, Plenum Press, 1994. Forexample, an acylated sugar can be coupled to a silylated base with alewis acid, such as tin tetrachloride, titanium tetrachloride ortrimethylsilyltriflate in the appropriate solvent at a suitabletemperature. Alternatively, a halo-sugar can be coupled to a silylatedbase with the presence of trimethylsilyltriflate.

Subsequently, the nucleoside can be deprotected by methods well known tothose skilled in the art, as taught by Greene et al. Protective Groupsin Organic Synthesis, John Wiley and Sons, Second Edition, 1991.

In a particular embodiment, the 2′-C-branched ribonucleoside is desired.The synthesis of a ribonucleoside is shown in Scheme 3. Alternatively,deoxyribo-nucleoside is desired. To obtain these nucleosides, the formedribonucleoside can optionally be protected by methods well known tothose skilled in the art, as taught by Greene et al. Protective Groupsin Organic Synthesis, John Wiley and Sons, Second Edition, 1991, andthen the 2′-OH can be reduced with a suitable reducing agent.Optionally, the 2′-hydroxyl can be activated to facilitate reduction;i.e. via the Barton reduction.

2. Modification of a Pre-Formed Nucleoside

The key starting material for this process is an appropriatelysubstituted nucleoside with a 2′-OH and 2′-H. The nucleoside can bepurchased or can be prepared by any known means including standardcoupling techniques. The nucleoside can be optionally protected withsuitable protecting groups, preferably with acyl or silyl groups, bymethods well known to those skilled in the art, as taught by Greene etal. Protective Groups in Organic Synthesis, John Wiley and Sons, SecondEdition, 1991.

The appropriately protected nucleoside can then be oxidized with theappropriate oxidizing agent in a compatible solvent at a suitabletemperature to yield the 2′-modified sugar. Possible oxidizing agentsare Jones reagent (a mixture of chromic acid and sulfuric acid),Collins's reagent (dipyridine Cr(VI) oxide, Corey's reagent (pyridiniumchlorochromate), pyridinium dichromate, acid dichromate, potassiumpermanganate, MnO₂, ruthenium tetroxide, phase transfer catalysts suchas chromic acid or permanganate supported on a polymer, Cl₂-pyridine,H₂O₂-ammonium molybdate, NaBrO₂—CAN, NaOCl in HOAc, copper chromite,copper oxide, Raney nickel, palladium acetate, Meerwin-Pondorf Verleyreagent (aluminum t-butoxide with another ketone) andN-bromosuccinimide.

Subsequently, the nucleoside can be deprotected by methods well known tothose skilled in the art, as taught by Greene-Greene et al. ProtectiveGroups in Organic Synthesis, John Wiley and Sons, Second Edition, 1991.

In a particular embodiment, the 2′-C-branched ribonucleoside is desired.The synthesis of a ribonucleoside is shown in Scheme 4. Alternatively,deoxyribo-nucleoside is desired. To obtain these nucleosides, the formedribonucleoside can optionally be protected by methods well known tothose skilled in the art, as taught by Greene et al. Protective Groupsin Organic Synthesis, John Wiley and Sons, Second Edition, 1991, andthen the 2′-OH can be reduced with a suitable reducing agent.Optionally, the 2′-hydroxyl can be activated to facilitate reduction;i.e. via the Barton reduction.

In another embodiment of the invention, the L-enantiomers are desired.Therefore, the L-enantiomers can be corresponding to the compounds ofthe invention can be prepared following the same foregoing generalmethods, beginning with the corresponding L-sugar or nucleosideL-enantiomer as starting material.

C. General Synthesis of 3′-C-Branched Nucleosides

3′-C-Branched ribonucleosides of the following structure:

wherein BASE is a purine or pyrimidine base as defined herein;

-   R⁷ and R⁹ are independently hydrogen, OR², hydroxy, alkyl (including    lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl,    —C(O)O(alkyl), —C(O)O(lower alkyl), —O(acyl), —O(lower acyl),    —O(alkyl), —O(lower alkyl), —O(alkenyl), chlorine, bromine, iodine,    NO₂, NH₂, —NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂;-   R⁸ is H, alkyl (including lower alkyl), chlorine, bromine or iodine;    alternatively, R⁷ and R⁹, or R⁸ and R⁹ can come together to form a    pi bond;-   R¹ and R² are independently H; phosphate (including monophosphate,    diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl    (including lower acyl); alkyl (including lower alkyl); sulfonate    ester including alkyl or arylalkyl sulfonyl including    methanesulfonyl and benzyl, wherein the phenyl group is optionally    substituted with one or more substituents as described in the    definition of aryl given herein; a lipid, including a phospholipid;    an amino acid; a carbohydrate; a peptide; a cholesterol; or other    pharmaceutically acceptable leaving group which when administered in    vivo is capable of providing a compound wherein R¹ or R² is    independently H or phosphate;-   R⁶ is an alkyl, chloro-, fluoro-, bromo-, iodo-alkyl (i.e. CF₃),    alkenyl, or alkynyl (i.e. allyl); and-   X is O, S, SO₂ or CH₂    can be prepared by one of the following general methods.    1. Glycosylation of the Nucleobase with an Appropriately Modified    Sugar

The key starting material for this process is an appropriatelysubstituted sugar with a 3′-OH and 3′-H, with the appropriate leavinggroup (LG), for example an acyl group or a chloro, bromo, fluoro, iodo.The sugar can be purchased or can be prepared by any known meansincluding standard epimerization, substitution, oxidation and reductiontechniques. The substituted sugar can then be oxidized with theappropriate oxidizing agent in a compatible solvent at a suitabletemperature to yield the 3′-modified sugar. Possible oxidizing agentsare Jones reagent (a mixture of chromic acid and sulfuric acid),Collins's reagent (dipyridine Cr(VI) oxide, Corey's reagent (pyridiniumchlorochromate), pyridinium dichromate, acid dichromate, potassiumpermanganate, MnO₂, ruthenium tetroxide, phase transfer catalysts suchas chromic acid or permanganate supported on a polymer, Cl₂-pyridine,H₂O₂-ammonium molybdate, NaBrO₂—CAN, NaOCl in HOAc, copper chromite,copper oxide, Raney nickel, palladium acetate, Meerwin-Pondorf-Verleyreagent (aluminum t-butoxide with another ketone) and N-bromosuccimmide.

Then coupling of an organometallic carbon nucleophile, such as aGrignard reagent, an organolithium, lithium dialkylcopper or R⁶—SiMe₃ inTBAF with the ketone with the appropriate non-protic solvent at asuitable temperature, yields the 3′-C-branched sugar. The 3′-C-branchedsugar can be optionally protected with a suitable protecting group,preferably with an acyl or silyl group, by methods well known to thoseskilled in the art, as taught by Greene et al. Protective Groups inOrganic Synthesis, John Wiley and Sons, Second Edition, 1991.

The optionally protected sugar can then be coupled to the BASE bymethods well known to those skilled in the art, as taught by TownsendChemistry of Nucleosides and Nucleotides, Plenum Press, 1994. Forexample, an acylated sugar can be coupled to a silylated base with alewis acid, such as tin tetrachloride, titanium tetrachloride ortrimethylsilyltriflate in the appropriate solvent at a suitabletemperature. Alternatively, a halo-sugar can be coupled to a silylatedbase with the presence of trimethylsilyltriflate.

Subsequently, the nucleoside can be deprotected by methods well known tothose skilled in the art, as taught by Greene et al. Protective Groupsin Organic Synthesis, John Wiley and Sons, Second Edition, 1991.

In a particular embodiment, the 3′-C-branched ribonucleoside is desired.The synthesis of a ribonucleoside is shown in Scheme 5. Alternatively,deoxyribo-nucleoside is desired. To obtain these nucleosides, the formedribonucleoside can optionally be protected by methods well known tothose skilled in the art, as taught by Greene et al. Protective Groupsin Organic Synthesis, John Wiley and Sons, Second Edition, 1991, andthen the 2′-OH can be reduced with a suitable reducing agent.Optionally, the 2′-hydroxyl can be activated to facilitate reduction;i.e. via the Barton reduction.

2. Modification of a Pre-Formed Nucleoside

The key starting material for this process is an appropriatelysubstituted nucleoside with a 3′-OH and 3′-H. The nucleoside can bepurchased or can be prepared by any known means including standardcoupling techniques. The nucleoside can be optionally protected withsuitable protecting groups, preferably with acyl or silyl groups, bymethods well known to those skilled in the art, as taught by Greene etal. Protective Groups in Organic Synthesis, John Wiley and Sons, SecondEdition, 1991.

The appropriately protected nucleoside can then be oxidized with theappropriate oxidizing agent in a compatible solvent at a suitabletemperature to yield the 2′-modified sugar. Possible oxidizing agentsare Jones reagent (a mixture of chromic acid and sulfuric acid),Collins's reagent (dipyridine Cr(VI) oxide, Corey's reagent (pyridiniumchlorochromate), pyridinium dichromate, acid dichromate, potassiumpermanganate, MnO₂, ruthenium tetroxide, phase transfer catalysts suchas chromic acid or permanganate supported on a polymer, Cl₂-pyridine,H₂O₂-ammonium molybdate, NaBrO₂—CAN, NaOCl in HOAc, copper chromite,copper oxide, Raney nickel, palladium acetate, Meerwin-Pondorf-Verleyreagent (aluminum t-butoxide with another ketone) andN-bromosuccinimide.

Subsequently, the nucleoside can be deprotected by methods well known tothose skilled in the art, as taught by Greene-Greene et al. ProtectiveGroups in Organic Synthesis, John Wiley and Sons, Second Edition, 1991.

In a particular embodiment, the 3′-C-branched ribonucleoside is desired.The synthesis of a ribonucleoside is shown in Scheme 6. Alternatively,deoxyribo-nucleoside is desired. To obtain these nucleosides, the formedribonucleoside can optionally be protected by methods well known tothose skilled in the art, as taught by Greene et al. Protective Groupsin Organic Synthesis, John Wiley and Sons, Second Edition, 1991, andthen the 2′-OH can be reduced with a suitable reducing agent.Optionally, the 2′-hydroxyl can be activated to facilitate reduction;i.e. via the Barton reduction.

In another embodiment of the invention, the L-enantiomers are desired.Therefore, the L-enantiomers can be corresponding to the compounds ofthe invention can be prepared following the same foregoing generalmethods, beginning with the corresponding L-sugar or nucleosideL-enantiomer as starting material.

EXAMPLES Example 1 Preparation of 1′-C-methylriboadenine via6-amino-9-(1-deoxy-β-D-psicofuranosyl)purine

As another alternative method of preparation, the title compound couldalso be prepared according to a published procedure (J. Farkas, and F.Sorm, “Nucleic acid components and their analogues. XCIV. Synthesis of6-amino-9-(1-deoxy-β-D-psicofuranosyl)purine”, Collect. Czech. Chem.Commun. 1967, 32, 2663-2667. J. Farkas”, Collect. Czech. Chem. Commun.1966, 31, 1535) (Scheme 7).

In a similar manner, but using the appropriate sugar and pyrimidine orpurine bases, the following nucleosides of Formula I are prepared.

wherein: R¹ R² R³ X¹ X² Y H H H H H H H H H H H NH₂ H H H H HNH-cyclopropyl H H H H H NH-methyl H H H H H NH-ethyl H H H H HNH-acetyl H H H H H OH H H H H H OMe H H H H H OEt H H H H HO-cyclopropyl H H H H H O-acetyl H H H H H SH H H H H H SMe H H H H HSEt H H H H H S-cyclopropyl H H H H H F H H H H H Cl H H H H H Br H H HH H I monophosphate H H H H NH₂ monophosphate H H H H NH-acetylmonophosphate H H H H NH-cyclopropyl monophosphate H H H H NH-methylmonophosphate H H H H NH-ethyl monophosphate H H H H OH monophosphate HH H H O-acetyl monophosphate H H H H OMe monophosphate H H H H OEtmonophosphate H H H H O-cyclopropyl monophosphate H H H H SHmonophosphate H H H H SMe monophosphate H H H H SEt monophosphate H H HH S-cyclopropyl monophosphate H H H H F monophosphate H H H H Clmonophosphate H H H H Br monophosphate H H H H I diphosphate H H H H NH₂diphosphate H H H H NH-acetyl diphosphate H H H H NH-cyclopropyldiphosphate H H H H NH-methyl diphosphate H H H H NH-ethyl diphosphate HH H H OH diphosphate H H H H O-acetyl diphosphate H H H H OMediphosphate H H H H OEt diphosphate H H H H O-cyclopropyl diphosphate HH H H SH diphosphate H H H H SMe diphosphate H H H H SEt diphosphate H HH H S-cyclopropyl diphosphate H H H H F diphosphate H H H H Cldiphosphate H H H H Br diphosphate H H H H I triphosphate H H H H NH₂triphosphate H H H H NH-acetyl triphosphate H H H H NH-cyclopropyltriphosphate H H H H NH-methyl triphosphate H H H H NH-ethyltriphosphate H H H H OH triphosphate H H H H OMe triphosphate H H H HOEt triphosphate H H H H O-cyclopropyl triphosphate H H H H O-acetyltriphosphate H H H H SH triphosphate H H H H SMe triphosphate H H H HSEt triphosphate H H H H S-cyclopropyl triphosphate H H H H Ftriphosphate H H H H Cl triphosphate H H H H Br triphosphate H H H H Imonophosphate monophosphate monophosphate H H NH₂ monophosphatemonophosphate monophosphate H H NH-cyclopropyl monophosphatemonophosphate monophosphate H H OH monophosphate monophosphatemonophosphate H H F monophosphate monophosphate monophosphate H H Cldiphosphate diphosphate diphosphate H H NH₂ diphosphate diphosphatediphosphate H H NH-cyclopropyl diphosphate diphosphate diphosphate H HOH diphosphate diphosphate diphosphate H H F diphosphate diphosphatediphosphate H H Cl triphosphate triphosphate triphosphate H H NH₂triphosphate triphosphate triphosphate H H NH-cyclopropyl triphosphatetriphosphate triphosphate H H OH triphosphate triphosphate triphosphateH H F triphosphate triphosphate triphosphate H H Cl H H H F H NH₂ H H HF H NH-cyclopropyl H H H F H OH H H H F H F H H H F H Cl H H H Cl H NH₂H H H Cl H NH-cyclopropyl H H H Cl H OH H H H Cl H F H H H Cl H Cl H H HBr H NH₂ H H H Br H NH-cyclopropyl H H H Br H OH H H H Br H F H H H Br HCl H H H NH₂ H NH₂ H H H NH₂ H NH-cyclopropyl H H H NH₂ H OH H H H NH₂ HF H H H NH₂ H Cl H H H SH H NH₂ H H H SH H NH-cyclopropyl H H H SH H OHH H H SH H F H H H SH H Cl acetyl H H H H NH₂ acetyl H H H HNH-cyclopropyl acetyl H H H H OH acetyl H H H H F acetyl H H H H Clacetyl H H F H NH₂ acetyl H H F H NH-cyclopropyl acetyl H H F H OHacetyl H H F H F acetyl H H F H Cl H acetyl acetyl H H NH₂ H acetylacetyl H H NH-cyclopropyl H acetyl acetyl H H OH H acetyl acetyl H H F Hacetyl acetyl H H Cl acetyl acetyl acetyl H H NH₂ acetyl acetyl acetyl HH NH-cyclopropyl acetyl acetyl acetyl H H OH acetyl acetyl acetyl H H Facetyl acetyl acetyl H H Cl monophosphate acetyl acetyl H H NH₂monophosphate acetyl acetyl H H NH-cyclopropyl monophosphate acetylacetyl H H OH monophosphate acetyl acetyl H H F monophosphate acetylacetyl H H Cl diphosphate acetyl acetyl H H NH₂ diphosphate acetylacetyl H H NH-cyclopropyl diphosphate acetyl acetyl H H OH diphosphateacetyl acetyl H H F diphosphate acetyl acetyl H H Cl triphosphate acetylacetyl H H NH₂ triphosphate acetyl acetyl H H NH-cyclopropyltriphosphate acetyl acetyl H H OH triphosphate acetyl acetyl H H Ftriphosphate acetyl acetyl H H Cl H H H H NH₂ H H H H H NH₂ NH₂ H H H HNH₂ NH-cyclopropyl H H H H NH₂ NH-methyl H H H H NH₂ NH-ethyl H H H HNH₂ NH-acetyl H H H H NH₂ OH H H H H NH₂ OMe H H H H NH₂ OEt H H H H NH₂O-cyclopropyl H H H H NH₂ O-acetyl H H H H NH₂ SH H H H H NH₂ SMe H H HH NH₂ SEt H H H H NH₂ S-cyclopropyl H H H H NH₂ F H H H H NH₂ Cl H H H HNH₂ Br H H H H NH₂ I monophosphate H H H NH₂ NH₂ monophosphate H H H NH₂NH-acetyl monophosphate H H H NH₂ NH-cyclopropyl monophosphate H H H NH₂NH-methyl monophosphate H H H NH₂ NH-ethyl monophosphate H H H NH₂ OHmonophosphate H H H NH₂ O-acetyl monophosphate H H H NH₂ OMemonophosphate H H H NH₂ OEt monophosphate H H H NH₂ O-cyclopropylmonophosphate H H H NH₂ SH monophosphate H H H NH₂ SMe monophosphate H HH NH₂ SEt monophosphate H H H NH₂ S-cyclopropyl monophosphate H H H NH₂F monophosphate H H H NH₂ Cl monophosphate H H H NH₂ Br monophosphate HH H NH₂ I diphosphate H H H NH₂ NH₂ diphosphate H H H NH₂ NH-acetyldiphosphate H H H NH₂ NH-cyclopropyl diphosphate H H H NH₂ NH-methyldiphosphate H H H NH₂ NH-ethyl diphosphate H H H NH₂ OH diphosphate H HH NH₂ O-acetyl diphosphate H H H NH₂ OMe diphosphate H H H NH₂ OEtdiphosphate H H H NH₂ O-cyclopropyl diphosphate H H H NH₂ SH diphosphateH H H NH₂ SMe diphosphate H H H NH₂ SEt diphosphate H H H NH₂S-cyclopropyl diphosphate H H H NH₂ F diphosphate H H H NH₂ Cldiphosphate H H H NH₂ Br diphosphate H H H NH₂ I triphosphate H H H NH₂NH₂ triphosphate H H H NH₂ NH-acetyl triphosphate H H H NH₂NH-cyclopropyl triphosphate H H H NH₂ NH-methyl triphosphate H H H NH₂NH-ethyl triphosphate H H H NH₂ OH triphosphate H H H NH₂ OMetriphosphate H H H NH₂ OEt triphosphate H H H NH₂ O-cyclopropyltriphosphate H H H NH₂ O-acetyl triphosphate H H H NH₂ SH triphosphate HH H NH₂ SMe triphosphate H H H NH₂ SEt triphosphate H H H NH₂S-cyclopropyl triphosphate H H H NH₂ F triphosphate H H H NH₂ Cltriphosphate H H H NH₂ Br triphosphate H H H NH₂ I monophosphatemonophosphate monophosphate H NH₂ NH₂ monophosphate monophosphatemonophosphate H NH₂ NH-cyclopropyl monophosphate monophosphatemonophosphate H NH₂ OH monophosphate monophosphate monophosphate H NH₂ Fmonophosphate monophosphate monophosphate H NH₂ Cl diphosphatediphosphate diphosphate H NH₂ NH₂ diphosphate diphosphate diphosphate HNH₂ NH-cyclopropyl diphosphate diphosphate diphosphate H NH₂ OHdiphosphate diphosphate diphosphate H NH₂ F diphosphate diphosphatediphosphate H NH₂ Cl triphosphate triphosphate triphosphate H NH₂ NH₂triphosphate triphosphate triphosphate H NH₂ NH-cyclopropyl triphosphatetriphosphate triphosphate H NH₂ OH triphosphate triphosphatetriphosphate H NH₂ F triphosphate triphosphate triphosphate H NH₂ Cl H HH F NH₂ NH₂ H H H F NH₂ NH-cyclopropyl H H H F NH₂ OH H H H F NH₂ F H HH F NH₂ Cl H H H Cl NH₂ NH₂ H H H Cl NH₂ NH-cyclopropyl H H H Cl NH₂ OHH H H Cl NH₂ F H H H Cl NH₂ Cl H H H Br NH₂ NH₂ H H H Br NH₂NH-cyclopropyl H H H Br NH₂ OH H H H Br NH₂ F H H H Br NH₂ Cl H H H NH₂NH₂ NH₂ H H H NH₂ NH₂ NH-cyclopropyl H H H NH₂ NH₂ OH H H H NH₂ NH₂ F HH H NH₂ NH₂ Cl H H H SH NH₂ NH₂ H H H SH NH₂ NH-cyclopropyl H H H SH NH₂OH H H H SH NH₂ F H H H SH NH₂ Cl acetyl H H H NH₂ NH₂ acetyl H H H NH₂NH-cyclopropyl acetyl H H H NH₂ OH acetyl H H H NH₂ F acetyl H H H NH₂Cl acetyl H H F NH₂ NH₂ acetyl H H F NH₂ NH-cyclopropyl acetyl H H F NH₂OH acetyl H H F NH₂ F acetyl H H F NH₂ Cl H acetyl acetyl H NH₂ NH₂ Hacetyl acetyl H NH₂ NH-cyclopropyl H acetyl acetyl H NH₂ OH H acetylacetyl H NH₂ F H acetyl acetyl H NH₂ Cl acetyl acetyl acetyl H NH₂ NH₂acetyl acetyl acetyl H NH₂ NH-cyclopropyl acetyl acetyl acetyl H NH₂ OHacetyl acetyl acetyl H NH₂ F acetyl acetyl acetyl H NH₂ Cl monophosphateacetyl acetyl H NH₂ NH₂ monophosphate acetyl acetyl H NH₂ NH-cyclopropylmonophosphate acetyl acetyl H NH₂ OH monophosphate acetyl acetyl H NH₂ Fmonophosphate acetyl acetyl H NH₂ Cl diphosphate acetyl acetyl H NH₂ NH₂diphosphate acetyl acetyl H MH₂ NH-cyclopropyl diphosphate acetyl acetylH NH₂ OH diphosphate acetyl acetyl H NH₂ F diphosphate acetyl acetyl HNH₂ Cl triphosphate acetyl acetyl H NH₂ NH₂ triphosphate acetyl acetyl HNH₂ NH-cyclopropyl triphosphate acetyl acetyl H NH₂ OH triphosphateacetyl acetyl H NH₂ F triphosphate acetyl acetyl H NH₂ Cl H H H H Cl H HH H H Cl H H H H H Cl NH₂ H H H H Cl NH-cyclopropyl H H H H Cl NH-methylH H H H Cl NH-ethyl H H H H Cl NH-acetyl H H H H Cl OH H H H H Cl OMe HH H H Cl OEt H H H H Cl O-cyclopropyl H H H H Cl O-acetyl H H H H Cl SHH H H H Cl SMe H H H H Cl SEt H H H H Cl S-cyclopropyl monophosphate H HH Cl NH₂ monophosphate H H H Cl NH-acetyl monophosphate H H H ClNH-cyclopropyl monophosphate H H H Cl NH-methyl monophosphate H H H ClNH-ethyl monophosphate H H H Cl OH monophosphate H H H Cl O-acetylmonophosphate H H H Cl OMe monophosphate H H H Cl OEt monophosphate H HH Cl O-cyclopropyl monophosphate H H H Cl SH monophosphate H H H Cl SMemonophosphate H H H Cl SEt monophosphate H H H Cl S-cyclopropyldiphosphate H H H Cl NH₂ diphosphate H H H Cl NH-acetyl diphosphate H HH Cl NH-cyclopropyl diphosphate H H H Cl NH-methyl diphosphate H H H ClNH-ethyl diphosphate H H H Cl OH diphosphate H H H Cl O-acetyldiphosphate H H H Cl OMe diphosphate H H H Cl OEt diphosphate H H H ClO-cyclopropyl diphosphate H H H Cl SH diphosphate H H H Cl SMediphosphate H H H Cl SEt diphosphate H H H Cl S-cyclopropyl triphosphateH H H Cl NH₂ triphosphate H H H Cl NH-acetyl triphosphate H H H ClNH-cyclopropyl triphosphate H H H Cl NH-methyl triphosphate H H H ClNH-ethyl triphosphate H H H Cl OH triphosphate H H H Cl OMe triphosphateH H H Cl OEt triphosphate H H H Cl O-cyclopropyl triphosphate H H H ClO-acetyl triphosphate H H H Cl SH triphosphate H H H Cl SMe triphosphateH H H Cl SEt triphosphate H H H Cl S-cyclopropyl monophosphatemonophosphate monophosphate H Cl NH₂ monophosphate monophosphatemonophosphate H Cl NH-cyclopropyl monophosphate monophosphatemonophosphate H Cl OH diphosphate diphosphate diphosphate H Cl NH₂diphosphate diphosphate diphosphate H Cl NH-cyclopropyl diphosphatediphosphate diphosphate H Cl OH triphosphate triphosphate triphosphate HCl NH₂ triphosphate triphosphate triphosphate H Cl NH-cyclopropyltriphosphate triphosphate triphosphate H Cl OH H H H F Cl NH₂ H H H F ClNH-cyclopropyl H H H F Cl OH H H H Cl Cl NH₂ H H H Cl Cl NH-cyclopropylH H H Cl Cl OH H H H Br Cl NH₂ H H H Br Cl NH-cyclopropyl H H H Br Cl OHH H H NH₂ Cl NH₂ H H H NH₂ Cl NH-cyclopropyl H H H NH₂ Cl OH H H H SH ClNH₂ H H H SH Cl NH-cyclopropyl H H H SH Cl OH acetyl H H H Cl NH₂ acetylH H H Cl NH-cyclopropyl acetyl H H H Cl OH acetyl H H F Cl NH₂ acetyl HH F Cl NH-cyclopropyl acetyl H H F Cl OH H acetyl acetyl H Cl NH₂ Hacetyl acetyl H Cl NH-cyclopropyl H acetyl acetyl H Cl OH acetyl acetylacetyl H Cl NH₂ acetyl acetyl acetyl H Cl NH-cyclopropyl acetyl acetylacetyl H Cl OH monophosphate acetyl acetyl H Cl NH₂ monophosphate acetylacetyl H Cl NH-cyclopropyl monophosphate acetyl acetyl H Cl OHdiphosphate acetyl acetyl H Cl NH₂ diphosphate acetyl acetyl H ClNH-cyclopropyl diphosphate acetyl acetyl H Cl OH triphosphate acetylacetyl H Cl NH₂ triphosphate acetyl acetyl H Cl NH-cyclopropyltriphosphate acetyl acetyl H Cl OH H H H H Cl NH₂ H H H H ClNH-cyclopropyl H H H H Cl OH H H H H Br NH₂ H H H H Br NH-cyclopropyl HH H H Br OH

Alternatively, the following nucleosides of Formula IV are prepared,using the appropriate sugar and pyrimidine or purine bases.

wherein: R¹ R² R³ X¹ Y H H H H H H H H H NH₂ H H H H NH-cyclopropyl H HH H NH-methyl H H H H NH-ethyl H H H H NH-acetyl H H H H OH H H H H OMeH H H H OEt H H H H O-cyclopropyl H H H H O-acetyl H H H H SH H H H HSMe H H H H SEt H H H H S-cyclopropyl monophosphate H H H NH₂monophosphate H H H NH-acetyl monophosphate H H H NH-cyclopropylmonophosphate H H H NH-methyl monophosphate H H H NH-ethyl monophosphateH H H OH monophosphate H H H O-acetyl monophosphate H H H OMemonophosphate H H H OEt monophosphate H H H O-cyclopropyl monophosphateH H H SH monophosphate H H H SMe monophosphate H H H SEt monophosphate HH H S-cyclopropyl diphosphate H H H NH₂ diphosphate H H H NH-acetyldiphosphate H H H NH-cyclopropyl diphosphate H H H NH-methyl diphosphateH H H NH-ethyl diphosphate H H H OH diphosphate H H H O-acetyldiphosphate H H H OMe diphosphate H H H OEt diphosphate H H HO-cyclopropyl diphosphate H H H SH diphosphate H H H SMe diphosphate H HH SEt diphosphate H H H S-cyclopropyl triphosphate H H H NH₂triphosphate H H H NH-acetyl triphosphate H H H NH-cyclopropyltriphosphate H H H NH-methyl triphosphate H H H NH-ethyl triphosphate HH H OH triphosphate H H H OMe triphosphate H H H OEt triphosphate H H HO-cyclopropyl triphosphate H H H O-acetyl triphosphate H H H SHtriphosphate H H H SMe triphosphate H H H SEt triphosphate H H HS-cyclopropyl monophosphate monophosphate monophosphate H NH₂monophosphate monophosphate monophosphate H NH-cyclopropyl monophosphatemonophosphate monophosphate H OH diphosphate diphosphate diphosphate HNH₂ diphosphate diphosphate diphosphate H NH-cyclopropyl diphosphatediphosphate diphosphate H OH triphosphate triphosphate triphosphate HNH₂ triphosphate triphosphate triphosphate H NH-cyclopropyl triphosphatetriphosphate triphosphate H OH H H H F NH₂ H H H F NH-cyclopropyl H H HF OH H H H Cl NH₂ H H H Cl NH-cyclopropyl H H H Cl OH H H H Br NH₂ H H HBr NH-cyclopropyl H H H Br OH H H H NH₂ NH₂ H H H NH₂ NH-cyclopropyl H HH NH₂ OH H H H SH NH₂ H H H SH NH-cyclopropyl H H H SH OH acetyl H H HNH₂ acetyl H H H NH-cyclopropyl acetyl H H H OH acetyl H H F NH₂ acetylH H F NH-cyclopropyl acetyl H H F OH H acetyl acetyl H NH₂ H acetylacetyl H NH-cyclopropyl H acetyl acetyl H OH acetyl acetyl acetyl H NH₂acetyl acetyl acetyl H NH-cyclopropyl acetyl acetyl acetyl H OHmonophosphate acetyl acetyl H NH₂ monophosphate acetyl acetyl HNH-cyclopropyl monophosphate acetyl acetyl H OH diphosphate acetylacetyl H NH₂ diphosphate acetyl acetyl H NH-cyclopropyl diphosphateacetyl acetyl H OH triphosphate acetyl acetyl H NH₂ triphosphate acetylacetyl H NH-cyclopropyl triphosphate acetyl acetyl H OH

Alternatively, the following nucleosides of Formula VII are prepared,using the appropriate sugar and pyrimidine or purine bases.

wherein: R¹ R² R³ R⁶ X Base H H H CH₃ O 2,4-O- Diacetyluracil H H H CH₃O Hypoxanthine H H H CH₃ O 2,4-O- Diacetylthymine H H H CH₃ O Thymine HH H CH₃ O Cytosine H H H CH₃ O 4-(N-mono- acetyl)cytosine H H H CH₃ O4-(N,N- diacetyl)cytosine H H H CH₃ O Uracil H H H CH₃ O 5-FluorouracilH H H CH₃ S 2,4-O- Diacetyluraci H H H CH₃ S Hypoxanthine H H H CH₃ S2,4-O- Diacetylthymine H H H CH₃ S Thymine H H H CH₃ S Cytosine H H HCH₃ S 4-(N-mono- acetyl)cytosine H H H CH₃ S 4-(N,N- diacetyl)cytosine HH H CH₃ S Uracil H H H CH₃ S 5-Fluorouracil monophosphate H H CH₃ O2,4-O- Diacetyluracil monophosphate H H CH₃ O Hypoxanthine monophosphateH H CH₃ O 2,4-O- Diacetylthym monophosphate H H CH₃ O Thyminemonophosphate H H CH₃ O Cytosine monophosphate H H CH₃ O 4-(N-mono-acetyl)cytosine monophosphate H H CH₃ O 4-(N,N- diacetyl)cytosinemonophosphate H H CH₃ O Uracil monophosphate H H CH₃ O 5-Fluorouracilmonophosphate H H CH₃ S 2,4-O- Diacetyluracil monophosphate H H CH₃ SHypoxanthine monophosphate H H CH₃ S 2,4-O- Diacetylthym monophosphate HH CH₃ S Thymine monophosphate H H CH₃ S Cytosine monophosphate H H CH₃ S4-(N-mono- acetyl)cytosine monophosphate H H CH₃ S 4-(N,N-diacetyl)cytosine monophosphate H H CH₃ S Uracil monophosphate H H CH₃ S5-Fluorouracil diphosphate H H CH₃ O 2,4-O- Diacetyluracil diphosphate HH CH₃ O Hypoxanthine diphosphate H H CH₃ O 2,4-O- Diacetylthyminediphosphate H H CH₃ O Thymine diphosphate H H CH₃ O Cytosine diphosphateH H CH₃ O 4-(N-mono- acetyl)cytosine diphosphate H H CH₃ O 4-(N,N-diacetyl)cytosine diphosphate H H CH₃ O Uracil diphosphate H H CH₃ O5-Fluorouracil diphosphate H H CH₃ S 2,4-O- Diacetyluracil diphosphate HH CH₃ S Hypoxanthine diphosphate H H CH₃ S 2,4-O- Diacetylthymdiphosphate H H CH₃ S Thymine diphosphate H H CH₃ S Cytosinetriphosphate H H CH₃ O 2,4-O- Diacetyluracil triphosphate H H CH₃ OHypoxanthine triphosphate H H CH₃ O 2,4-O- Diacetylthymine triphosphateH H CH₃ O Thymine triphosphate H H CH₃ O Cytosine triphosphate H H CH₃ O4-(N-mono- acetyl)cytosine triphosphate H H CH₃ O 4-(N,N-diacetyl)cytosine triphosphate H H CH₃ O Uracil triphosphate H H CH₃ O5-Fluorouracil triphosphate H H CH₃ S 2,4-O- Diacetyluracil triphosphateH H CH₃ S Hypoxanthine triphosphate H H CH₃ S 2,4-O- Diacetylthyminetriphosphate H H CH₃ S Thymine triphosphate H H CH₃ S Cytosinemonophosphate monophosphate monophosphate CF₃ O 2,4-O- Diacetyluracilmonophosphate monophosphate monophosphate CF₃ O Hypoxanthinemonophosphate monophosphate monophosphate CF₃ O 2,4-O- Diacetylthyminemonophosphate monophosphate monophosphate CF₃ O Thymine monophosphatemonophosphate monophosphate CF₃ O Cytosine monophosphate monophosphatemonophosphate CF₃ O 4-(N-mono- acetyl)cytosine monophosphatemonophosphate monophosphate CF₃ O 4-(N,N- diacetyl)cytosinemonophosphate monophosphate monophosphate CF₃ O Uracil monophosphatemonophosphate monophosphate CF₃ O 5-Fluorouracil monophosphatemonophosphate monophosphate CF₃ S 2,4-O- Diacetyluracil monophosphatemonophosphate monophosphate CF₃ S Hypoxanthine monophosphatemonophosphate monophosphate CF₃ S 2,4-O- Diacetylthymine monophosphatemonophosphate monophosphate CF₃ S Thymine monophosphate monophosphatemonophosphate CF₃ S Cytosine monophosphate monophosphate monophosphateCF₃ S 4-(N-mono- acetyl)cytosine monophosphate monophosphatemonophosphate CF₃ S 4-(N,N- diacetyl)cytosine monophosphatemonophosphate monophosphate CF₃ S Uracil monophosphate monophosphatemonophosphate CF₃ S 5-Fluorouracil acetyl acetyl acetyl CF₃ O 4-(N,N-diacetyl)cytosine acetyl acetyl acetyl CF₃ S 4-(N,N- diacetyl)cytosineacetyl acetyl acetyl 2-bromo- O 4-(N,N- vinyl diacetyl)cytosine acetylacetyl acetyl 2-bromo- S 4-(N,N- vinyl diacetyl)cytosine H H H CH₃ O2-(N,N-diacetyl)- guanine H H H CH₃ O 6-O-acetyl guanine H H H CH₃ O8-fluoroguanine H H H CH₃ O guanine H H H CH₃ O 6-(N,N-diacetyl)-adenine H H H CH₃ O 2-fluoroadenine H H H CH₃ O 8-fluoroadenine H H HCH₃ O 2,8-difluoro- adenine H H H CH₃ O adenine H H H CH₃ S2-(N,N-diacetyl)- guanine H H H CH₃ S 6-O-acetyl guanine H H H CH₃ S8-fluoroguanine H H H CH₃ S guanine H H H CH₃ S 6-(N,N-diacetyl)-adenine H H H CH₃ S 2-fluoroadenine H H H CH₃ S 8-fluoroadenine H H HCH₃ S 2,8-difluoro- adenine H H H CH₃ S adenine monophosphate H H CH₃ O2-(N,N-diacetyl)- guanine monophosphate H H CH₃ O 6-O-acetyl guaninemonophosphate H H CH₃ O 8-fluoroguanine monophosphate H H CH₃ O guaninemonophosphate H H CH₃ O 6-(N,N-diacetyl)- adenine monophosphate H H CH₃O 2-fluoroadenine monophosphate H H CH₃ O 8-fluoroadenine monophosphateH H CH₃ O 2,8-difluoro- adenine monophosphate H H CH₃ O adeninemonophosphate H H CH₃ S 2-(N,N-diacetyl)- guanine monophosphate H H CH₃S 6-O-acetyl guanine monophosphate H H CH₃ S 8-fluoroguaninemonophosphate H H CH₃ S guanine monophosphate H H CH₃ S6-(N,N-diacetyl)- adenine monophosphate H H CH₃ S 2-fluoroadeninemonophosphate H H CH₃ S 8-fluoroadenine monophosphate H H CH₃ S2,8-difluoro- adenine monophosphate H H CH₃ S adenine diphosphate H HCH₃ O 2-(N,N-diacetyl)- guanine diphosphate H H CH₃ O 6-O-acetyl guaninediphosphate H H CH₃ O 8-fluoroguanine diphosphate H H CH₃ O guaninediphosphate H H CH₃ O 6-(N,N-diacetyl)- adenine diphosphate H H CH₃ O2-fluoroadenine diphosphate H H CH₃ O 8-fluoroadenine diphosphate H HCH₃ O 2,8-difluoro- adenine diphosphate H H CH₃ O adenine diphosphate HH CH₃ S 2-(N,N-diacetyl)- guanine diphosphate H H CH₃ S 6-O-acetylguanine diphosphate H H CH₃ S 8-fluoroguanine diphosphate H H CH₃ Sguanine diphosphate H H CH₃ S 6-(N,N-diacetyl)- adenine diphosphate H HCH₃ S 2-fluoroadenine diphosphate H H CH₃ S 8-fluoroadenine diphosphateH H CH₃ S 2,8-difluoro- adenine diphosphate H H CH₃ S adeninetriphosphate H H CH₃ O 2-(N,N-diacetyl)- guanine triphosphate H H CH₃ O6-O-acetyl guanine triphosphate H H CH₃ O 8-fluoroguanine triphosphate HH CH₃ O guanine triphosphate H H CH₃ O 6-(N,N-diacetyl)- adeninetriphosphate H H CH₃ O 2-fluoroadenine triphosphate H H CH₃ O8-fluoroadenine triphosphate H H CH₃ O 2,8-difluoro- adeninetriphosphate H H CH₃ O 2-(N,N-diacetyl)- guanine triphosphate H H CH₃ S6-O-acetyl guanine triphosphate H H CH₃ S 8-fluoroguanine triphosphate HH CH₃ S guanine triphosphate H H CH₃ S 6-(N,N-diacetyl)- adeninetriphosphate H H CH₃ S 2-fluoroadenine triphosphate H H CH₃ S8-fluoroadenine triphosphate H H CH₃ S 2,8-difluoro- adeninetriphosphate H H CH₃ S adenine monophosphate monophosphate monophosphateCF₃ O 2-(N,N-diacetyl)- guanine monophosphate monophosphatemonophosphate CF₃ O 6-O-acetyl guanine monophosphate monophosphatemonophosphate CF₃ O 8-fluoroguanine monophosphate monophosphatemonophosphate CF₃ O guanine monophosphate monophosphate monophosphateCF₃ O 6-(N,N-diacetyl)- adenine monophosphate monophosphatemonophosphate CF₃ O 2-fluoroadenine monophosphate monophosphatemonophosphate CF₃ O 8-fluoroadenine monophosphate monophosphatemonophosphate CF₃ O 2,8-difluoro- adenine monophosphate monophosphatemonophosphate CF₃ O adenine monophosphate monophosphate monophosphateCF₃ S 2-(N,N-diacetyl)- guanine monophosphate monophosphatemonophosphate CF₃ S 6-O-acetyl guanine monophosphate monophosphatemonophosphate CF₃ S 8-fluoroguanine monophosphate monophosphatemonophosphate CF₃ S guanine monophosphate monophosphate monophosphateCF₃ S 6-(N,N-diacetyl)- adenine monophosphate monophosphatemonophosphate CF₃ S 2-fluoroadenine monophosphate monophosphatemonophosphate CF₃ S 8-fluoroadenine monophosphate monophosphatemonophosphate CF₃ S 2,8-difluoro- adenine monophosphate monophosphatemonophosphate CF₃ S adenine acetyl acetyl acetyl CF₃ O guanine acetylacetyl acetyl CF₃ S guanine acetyl acetyl acetyl 2-bromo- O guaninevinyl acetyl acetyl acetyl 2-bromo- S guanine vinyl

Alternatively, the following nucleosides of Formula VIII are prepared,using the appropriate sugar and pyrimidine or purine bases.

R¹ R² R⁶ X Base H H CH₃ O 2,4-O-Diacetyluracil H H CH₃ O Hypoxanthine HH CH₃ O 2,4-O-Diacetylthymine H H CH₃ O Thymine H H CH₃ O Cytosine H HCH₃ O 4-(N-mono-acetyl)cytosine H H CH₃ O 4-(N,N-diacetyl)cytosine H HCH₃ O Uracil H H CH₃ O 5-Fluorouracil H H CH₃ S 2,4-O-Diacetyluracil H HCH₃ S Hypoxanthine H H CH₃ S 2,4-O-Diacetylthymine H H CH₃ S Thymine H HCH₃ S Cytosine H H CH₃ S 4-(N-mono-acetyl)cytosine H H CH₃ S4-(N,N-diacetyl)cytosine H H CH₃ S Uracil H H CH₃ S 5-Fluorouracilmonophosphate H CH₃ O 2,4-O-Diacetyluracil monophosphate H CH₃ OHypoxanthine monophosphate H CH₃ O 2,4-O-Diacetylthymine monophosphate HCH₃ O Thymine monophosphate H CH₃ O Cytosine monophosphate H CH₃ O4-(N-mono-acetyl)cytosine monophosphate H CH₃ O 4-(N,N-diacetyl)cytosinemonophosphate H CH₃ O Uracil monophosphate H CH₃ O 5-Fluorouracilmonophosphate H CH₃ S 2,4-O-Diacetyluracil monophosphate H CH₃ SHypoxanthine monophosphate H CH₃ S 2,4-O-Diacetylthymine monophosphate HCH₃ S Thymine monophosphate H CH₃ S Cytosine monophosphate H CH₃ S4-(N-mono-acetyl)cytosine monophosphate H CH₃ S 4-(N,N-diacetyl)cytosinemonophosphate H CH₃ S Uracil monophosphate H CH₃ S 5-Fluorouracildiphosphate H CH₃ O 2,4-O-Diacetyluracil diphosphate H CH₃ OHypoxanthine diphosphate H CH₃ O 2,4-O-Diacetylthymine diphosphate H CH₃O Thymine diphosphate H CH₃ O Cytosine diphosphate H CH₃ O4-(N-mono-acetyl)cytosine diphosphate H CH₃ O 4-(N,N-diacetyl)cytosinediphosphate H CH₃ O Uracil diphosphate H CH₃ O 5-Fluorouracildiphosphate H CH₃ S 2,4-O-Diacetyluracil diphosphate H CH₃ SHypoxanthine diphosphate H CH₃ S 2,4-O-Diacetylthymine diphosphate H CH₃S Thymine diphosphate H CH₃ S Cytosine diphosphate H CH₃ S4-(N-mono-acetyl)cytosine diphosphate H CH₃ S 4-(N,N-diacetyl)cytosinediphosphate H CH₃ S Uracil diphosphate H CH₃ S 5-Fluorouraciltriphosphate H CH₃ O 2,4-O-Diacetyluracil triphosphate H CH₃ OHypoxanthine triphosphate H CH₃ O 2,4-O-diacethylthymine triphosphate HCH₃ O Thymine triphosphate H CH₃ O Cytosine triphosphate H CH₃ O4-(N-mono-acetyl)cytosine triphosphate H CH₃ O 4-(N,N-diacetyl)cytosinetriphosphate H CH₃ O Uracil triphosphate H CH₃ O 5-Fluorouraciltriphosphate H CH₃ S 2,4-O-Diacetyluracil triphosphate H CH₃ SHypoxanthine triphosphate H CH₃ S 2,4-O-Diacetylthymine triphosphate HCH₃ S Thymine triphosphate H CH₃ S Cytosine triphosphate H CH₃ S4-(N-mono-acetyl)cytosine triphosphate H CH₃ S 4-(N,N-diacetyl)cytosinetriphosphate H CH₃ S Uracil triphosphate H CH₃ S 5-Fluorouracilmonophosphate monophosphate CF₃ O 2,4-O-Diacetyluracil monophosphatemonophosphate CF₃ O Hypoxanthine monophosphate monophosphate CF₃ O2,4-O-Diacetylthymine monophosphate monophosphate CF₃ O Thyminemonophosphate monophosphate CF₃ O Cytosine monophosphate monophosphateCF₃ O 4-(N-mono-acetyl)cytosine monophosphate monophosphate CF₃ O4-(N,N-diacetyl)cytosine monophosphate monophosphate CF₃ O Uracilmonophosphate monophosphate CF₃ O 5-Fluorouracil monophosphatemonophosphate CF₃ S 2,4-O-Diacetyluracil monophosphate monophosphate CF₃S Hypoxanthine monophosphate monophosphate CF₃ S 2,4-O-Diacetylthyminemonophosphate monophosphate CF₃ S Thymine monophosphate monophosphateCF₃ S Cytosine monophosphate monophosphate CF₃ S4-(N-mono-acetyl)cytosine monophosphate monophosphate CF₃ S4-(N,N-diacetyl)cytosine monophosphate monophosphate CF₃ S Uracilmonophosphate monophosphate CF₃ S 5-Fluorouracil acetyl acetyl CF₃ O4-(N,N-diacetyl)cytosine acetyl acetyl CF₃ S 4-(N,N-diacetyl)cytosineacetyl acetyl 2-bromo- O 4-(N,N-diacetyl)cytosine vinyl acetyl acetyl2-bromo- S 4-(N,N-diacetyl)cytosine vinyl H H CH₃ O2-(N,N-diacetyl)-guanine H H CH₃ O 6-O-acetyl guanine H H CH₃ O8-fluoroguanine H H CH₃ O guanine H H CH₃ O 6-(N,N-diacetyl)-adenine H HCH₃ O 2-fluoroadenine H H CH₃ O 8-fluoroadenine H H CH₃ O2,8-difluoro-adenine H H CH₃ O adenine H H CH₃ S2-(N,N-diacetyl)-guanine H H CH₃ S 6-O-acetyl guanine H H CH₃ S8-fluoroguanine H H CH₃ S guanine H H CH₃ S 6-(N,N-diacetyl)-adenine H HCH₃ S 2-fluoroadenine H H CH₃ S 8-fluoroadenine H H CH₃ S2,8-difluoro-adenine H H CH₃ S adenine monophosphate H CH₃ O2-(N,N-diacetyl)-guanine monophosphate H CH₃ O 6-O-acetyl guaninemonophosphate H CH₃ O 8-fluoroguanine monophosphate H CH₃ O guaninemonophosphate H CH₃ O 6-(N,N-diacetyl)-adenine monophosphate H CH₃ O2-fluoroadenine monophosphate H CH₃ O 8-fluoroadenine monophosphate HCH₃ O 2,8-difluoro-adenine monophosphate H CH₃ O adenine monophosphate HCH₃ S 2-(N,N-diacetyl)-guanine monophosphate H CH₃ S 6-O-acetyl guaninemonophosphate H CH₃ S 8-fluoroguanine monophosphate H CH₃ S guaninemonophosphate H CH₃ S 6-(N,N-diacetyl)-adenine monophosphate H CH₃ S2-fluoroadenine monophosphate H CH₃ S 8-fluoroadenine monophosphate HCH₃ S 2,8-difluoro-adenine monophosphate H CH₃ S adenine diphosphate HCH₃ O 2-(N,N-diacetyl)-guanine diphosphate H CH₃ O 6-O-acetyl guaninediphosphate H CH₃ O 8-fluoroguanine diphosphate H CH₃ O guaninediphosphate H CH₃ O 6-(N,N-diacetyl)-adenine diphosphate H CH₃ O2-fluoroadenine diphosphate H CH₃ O 8-fluoroadenine diphosphate H CH₃ O2,8-difluoro-adenine diphosphate H CH₃ O adenine diphosphate H CH₃ S2-(N,N-diacetyl)-guanine diphosphate H CH₃ S 6-O-acetyl guaninediphosphate H CH₃ S 8-fluoroguanine diphosphate H CH₃ S guaninediphosphate H CH₃ S 6-(N,N-diacetyl)-adenine diphosphate H CH₃ S2-fluoroadenine diphosphate H CH₃ S 8-fluoroadenine diphosphate H CH₃ S2,8-difluoro-adenine diphosphate H CH₃ S adenine triphosphate H CH₃ O2-(N,N-diacetyl)-guanine triphosphate H CH₃ O 6-O-acetyl guaninetriphosphate H CH₃ O 8-fluoroguanine triphosphate H CH₃ O guaninetriphosphate H CH₃ O 6-(N,N-diacetyl)-adenine triphosphate H CH₃ O2-fluoroadenine triphosphate H CH₃ O 8-fluoroadenine triphosphate H CH₃O 2,8-difluoro-adenine triphosphate H CH₃ O adenine triphosphate H CH₃ S2-(N,N-diacetyl)-guanine triphosphate H CH₃ S 6-O-acetyl guaninetriphosphate H CH₃ S 8-fluoroguanine triphosphate H CH₃ S guaninetriphosphate H CH₃ S 6-(N,N-diacetyl)-adenine triphosphate H CH₃ S2-fluoroadenine triphosphate H CH₃ S 8-fluoroadenine triphosphate H CH₃S 2,8-difluoro-adenine triphosphate H CH₃ S adenine monophosphatemonophosphate CF₃ O 2-(N,N-diacetyl)-guanine monophosphate monophosphateCF₃ O 6-O-acetyl guanine monophosphate monophosphate CF₃ O8-fluoroguanine monophosphate monophosphate CF₃ O guanine monophosphatemonophosphate CF₃ O 6-(N,N-diacetyl)-adenine monophosphate monophosphateCF₃ O 2-fluoroadenine monophosphate monophosphate CF₃ O 8-fluoroadeninemonophosphate monophosphate CF₃ O 2,8-difluoro-adenine monophosphatemonophosphate CF₃ O adenine monophosphate monophosphate CF₃ S2-(N,N-diacetyl)-guanine monophosphate monophosphate CF₃ S 6-O-acetylguanine monophosphate monophosphate CF₃ S 8-fluoroguanine monophosphatemonophosphate CF₃ S guanine monophosphate monophosphate CF₃ S6-(N,N-diacetyl)-adenine monophosphate monophosphate CF₃ S2-fluoroadenine monophosphate monophosphate CF₃ S 8-fluoroadeninemonophosphate monophosphate CF₃ S 2,8-difluoro-adenine monophosphatemonophosphate CF₃ S adenine acetyl acetyl CF₃ O guanine acetyl acetylCF₃ S guanine acetyl acetyl 2-bromo- O guanine vinyl acetyl acetyl2-bromo- S guanine vinyl

Alternatively, the following nucleosides of Formula IX are prepared,using the appropriate sugar and pyrimidine or purine bases.

wherein: R¹ R⁶ X Base H CH₃ O 2,4-O-Diacetyluracil H CH₃ O HypoxanthineH CH₃ O 2,4-O-Diacetylthymine H CH₃ O Thymine H CH₃ O Cytosine H CH₃ O4-(N-mono-acetyl)cytosine H CH₃ O 4-(N,N-diacetyl)cytosine H CH₃ OUracil H CH₃ O 5-Fluorouracil H CH₃ S 2,4-O-Diacetyluracil H CH₃ SHypoxanthine H CH₃ S 2,4-O-Diacetylthymine H CH₃ S Thymine H CH₃ SCytosine H CH₃ S 4-(N-mono-acetyl)cytosine H CH₃ S4-(N,N-diacetyl)cytosine H CH₃ S Uracil H CH₃ S 5-Fluorouracilmonophosphate CH₃ O 2,4-O-Diacetyluracil monophosphate CH₃ OHypoxanthine monophosphate CH₃ O 2,4-O-Diacetylthymine monophosphate CH₃O Thymine monophosphate CH₃ O Cytosine monophosphate CH₃ O4-(N-mono-acetyl)cytosine monophosphate CH₃ O 4-(N,N-diacetyl)cytosinemonophosphate CH₃ O Uracil monophosphate CH₃ O 5-Fluorouracilmonophosphate CH₃ S 2,4-O-Diacetyluracil monophosphate CH₃ SHypoxanthine monophosphate CH₃ S 2,4-O-Diacetylthymine monophosphate CH₃S Thymine monophosphate CH₃ S Cytosine monophosphate CH₃ S4-(N-mono-acetyl)cytosine monophosphate CH₃ S 4-(N,N-diacetyl)cytosmonophosphate CH₃ S Uracil monophosphate CH₃ S 5-Fluorouracildiphosphate CH₃ O 2,4-O-Diacetyluracil diphosphate CH₃ O Hypoxanthinediphosphate CH₃ O 2,4-O-Diacetylthymine diphosphate CH₃ O Thyminediphosphate CH₃ O Cytosine diphosphate CH₃ O 4-(N-mono-acetyl)cytosinediphosphate CH₃ O 4-(N,N-diacetyl)cytosine diphosphate CH₃ O Uracildiphosphate CH₃ O 5-Fluorouracil diphosphate CH₃ S 2,4-O-Diacetyluracildiphosphate CH₃ S Hypoxanthine diphosphate CH₃ S 2,4-O-Diacetylthyminediphosphate CH₃ S Thymine diphosphate CH₃ S Cytosine triphosphate CH₃ O2,4-O-Diacetyluracil triphosphate CH₃ O Hypoxanthine triphosphate CH₃ O2,4-O-Diacetylthymine triphosphate CH₃ O Thymine triphosphate CH₃ OCytosine triphosphate CH₃ O 4-(N-mono-acetyl)cytosine triphosphate CH₃ O4-(N,N-diacetyl)cytosine triphosphate CH₃ O Uracil triphosphate CH₃ O5-Fluorouracil triphosphate CH₃ S 2,4-O-Diacetyluracil triphosphate CH₃S Hypoxanthine triphospahate CH₃ S 2,4-O-Diacetylthymine triphospahateCH₃ S Thymine triphospahate CH₃ S Cytosine monophosphate CF₃ O2,4-O-Diacetyluracil monophosphate CF₃ O Hypoxanthine monophosphate CF₃O 2,4-O-Diacetylthymine monophosphate CF₃ O Thymine monophosphate CF₃ OCytosine monophosphate CF₃ O 4-(N-mono-acetyl)cytosine monophosphate CF₃O 4-(N,N-diacetyl)cytos monophosphate CF₃ O Uracil monophosphate CF₃ O5-Fluorouracil monophosphate CF₃ S 2,4-O-Diacetyluracil monophosphateCF₃ S Hypoxanthine monophosphate CF₃ S 2,4-O-Diacetylthyminemonophosphate CF₃ S Thymine monophosphate CF₃ S Cytosine monophosphateCF₃ S 4-(N-mono-acetyl)cytosine monophosphate CF₃ S4-(N,N-diacetyl)cytosine monophosphate CF₃ S Uracil monophosphate CF₃ S5-Fluorouracil acetyl CF₃ O 4-(N,N-diacetyl)cytosine acetyl CF₃ S4-(N,N-diacetyl)cytosine acetyl 2-bromo-vinyl O 4-(N,N-diacetyl)cytosineacetyl 2-bromo-vinyl S 4-(N,N-diacetyl)cytosine

Alternatively, the following nucleosides of Formula XVI are prepared,using the appropriate sugar and pyrimidine or purine bases.

wherein: R¹ R⁶ R⁷ R⁸ X Base R¹⁰ R⁹ H CH₃ H H O 2,4-O-Diacetyluracil OHMe H CH₃ H H O Hypoxanthine OH Me H CH₃ H H O 2,4-O-Diacetylthymine OHMe H CH₃ H H O Thymine OH Me H CH₃ H H O Cytosine OH Me H CH₃ H H O4-(N-mono-acetyl)cytosine OH Me H CH₃ H H O 4-(N,N-diacetyl)cytosine OHMe H CH₃ H H O Uracil OH Me H CH₃ H H O 5-Fluorouracil OH Me H CH₃ H H S2,4-O-Diacetyluracil OH Me H CH₃ H H S Hypoxanthine OH Me H CH₃ H H S2,4-O-Diacetylthymine OH Me H CH₃ H H S Thymine OH Me H CH₃ H H SCytosine OH Me H CH₃ H H S 4-(N-mono-acetyl)cytosine OH Me H CH₃ H H S4-(N,N-diacetyl)cytosine OH Me H CH₃ H H S Uracil OH Me H CH₃ H H S5-Fluorouracil OH Me monophosphate CH₃ H H O 2,4-O-Diacetyluracil OH Memonophosphate CH₃ H H O Hypoxanthine OH Me monophosphate CH₃ H H O2,4-O-Diacetylthymine OH Me monophosphate CH₃ H H O Thymine OH Memonophosphate CH₃ H H O Cytosine OH Me monophosphate CH₃ H H O4-(N-mono-acetyl)cytosine OH Me monophosphate CH₃ H H O4-(N,N-diacetyl)cytosine OH Me monophosphate CH₃ H H O Uracil OH Memonophosphate CH₃ H H O 5-Fluorouracil OH Me monophosphate CH₃ H H S2,4-O-Diacetyluracil OH Me monophosphate CH₃ H H S Hypoxanthine OH Memonophosphate CH₃ H H S 2,4-O-Diacetylthymine OH Me monophosphate CH₃ HH S Thymine OH Me monophosphate CH₃ H H S Cytosine OH Me monophosphateCH₃ H H S 4-(N-mono-acetyl)cytosine OH Me monophosphate CH₃ H H S4-(N,N-diacetyl)cytosine OH Me monophosphate CH₃ H H S Uracil OH Memonophosphate CH₃ H H S 5-Fluorouracil OH Me diphosphate CH₃ H H O2,4-O-Diacetyluracil OH Me diphosphate CH₃ H H O Hypoxanthine OH Mediphosphate CH₃ H H O 2,4-O-Diacetylthymine OH Me diphosphate CH₃ H H OThymine OH Me diphosphate CH₃ H H O Cytosine OH Me diphosphate CH₃ H H O4-(N-mono-acetyl)cytosine OH Me diphosphate CH₃ H H O4-(N,N-diacetyl)cytosine OH Me diphosphate CH₃ H H O Uracil OH Mediphosphate CH₃ H H O 5-Fluorouracil OH Me diphosphate CH₃ H H S2,4-O-Diacetyluracil OH Me diphosphate CH₃ H H S Hypoxanthine OH Mediphosphate CH₃ H H S 2,4-O-Diacetylthymine OH Me diphosphate CH₃ H H SThymine OH Me diphosphate CH₃ H H S Cytosine OH Me triphosphate CH₃ H HO 2,4-O-Diacetyluracil OH Me triphosphate CH₃ H H O Hypoxanthine OH Metriphosphate CH₃ H H O 2,4-O-Diacetylthymine OH Me triphosphate CH₃ H HO Thymine OH Me triphosphate CH₃ H H O Cytosine OH Me triphosphate CH₃ HH O 4-(N-mono-acetyl)cytosine OH Me triphosphate CH₃ H H O4-(N,N-diacetyl)cytosine OH Me triphosphate CH₃ H H O Uracil OH Metriphosphate CH₃ H H O 5-Fluorouracil OH Me triphosphate CH₃ H H S2,4-O-Diacetyluracil OH Me triphosphate CH₃ H H S Hypoxanthine OH Metriphosphate CH₃ H H S 2,4-O-Diacetylthymine OH Me triphosphate CH₃ H HS Thymine OH Me triphosphate CH₃ H H S Cytosine OH Me monophosphate CF₃H H O 2,4-O-Diacetyluracil OH Me monophosphate CF₃ H H O Hypoxanthine OHMe monophosphate CF₃ H H O 2,4-O-Diacetylthymine OH Me monophosphate CF₃H H O Thymine OH Me monophosphate CF₃ H H O Cytosine OH Me monophosphateCF₃ H H O 4-(N-mono-acetyl)cytosine OH Me monophosphate CF₃ H H O4-(N,N-diacetyl)cytosine OH Me monophosphate CF₃ H H O Uracil OH Memonophosphate CF₃ H H O 5-Fluorouracil OH Me monophosphate CF₃ H H S2,4-O-Diacetyluracil OH Me monophosphate CF₃ H H S Hypoxanthine OH Memonophosphate CF₃ H H S 2,4-O-Diacetylthymine OH Me monophosphate CF₃ HH S Thymine OH Me monophosphate CF₃ H H S Cytosine OH Me monophosphateCF₃ H H S 4-(N-mono-acetyl)cytosine OH Me monophosphate CF₃ H H S4-(N,N-diacetyl)cytosine OH Me monophosphate CF₃ H H S Uracil OH Memonophosphate CF₃ H H S 5-Fluorouracil OH Me acetyl CH₃ H H O4-(N,N-diacetyl)cytosine H Br acetyl CH₃ H H S 4-(N,N-diacetyl)cytosineH Br acetyl CH₃ OH H O 4-(N,N-diacetyl)cytosine H Br acetyl CH₃ OH H S4-(N,N-diacetyl)cytosine H Br

Example 2 Preparation of 2′-C-methylriboadenine

The title compound was prepared according to a published procedure (R.E. Harry-O'kuru, J. M. Smith, and M. S. Wolfe, “A short, flexible routetoward 2′-C-branched ribonucleosides”, J. Org. Chem. 1997, 62,1754-1759) (Scheme 8).

In a similar manner, but using the appropriate sugar and pyrimidine orpurine bases, the following nucleosides of Formula II are prepared.

wherein: R¹ R² R³ X¹ X² Y H H H H H H H H H H H NH₂ H H H H HNH-cyclopropyl H H H H H NH-methyl H H H H H NH-ethyl H H H H HNH-acetyl H H H H H OH H H H H H OMe H H H H H OEt H H H H HO-cyclopropyl H H H H H O-acetyl H H H H H SH H H H H H SMe H H H H HSEt H H H H H S-cyclopropyl H H H H H F H H H H H Cl H H H H H Br H H HH H I monophosphate H H H H NH₂ monophosphate H H H H NH-acetylmonophosphate H H H H NH-cyclopropyl monophosphate H H H H NH-methylmonophosphate H H H H NH-ethyl monophosphate H H H H OH monophosphate HH H H O-acetyl monophosphate H H H H OMe monophosphate H H H H OEtmonophosphate H H H H O-cyclopropyl monophosphate H H H H SHmonophosphate H H H H SMe monophosphate H H H H SEt monophosphate H H HH S-cyclopropyl monophosphate H H H H F monophosphate H H H H Clmonophosphate H H H H Br monophosphate H H H H I diphosphate H H H H NH₂diphosphate H H H H NH-acetyl diphosphate H H H H NH-cyclopropyldiphosphate H H H H NH-methyl diphosphate H H H H NH-ethyl diphosphate HH H H OH diphosphate H H H H O-acetyl diphosphate H H H H OMediphosphate H H H H OEt diphosphate H H H H O-cyclopropyl diphosphate HH H H SH diphosphate H H H H SMe diphosphate H H H H SEt diphosphate H HH H S-cyclopropyl diphosphate H H H H F diphosphate H H H H Cldiphosphate H H H H Br diphosphate H H H H I triphosphate H H H H NH₂triphosphate H H H H NH-acetyl triphosphate H H H H NH-cyclopropyltriphosphate H H H H NH-methyl triphosphate H H H H NH-ethyltriphosphate H H H H OH triphosphate H H H H OMe triphosphate H H H HOEt triphosphate H H H H O-cyclopropyl triphosphate H H H H O-acetyltriphosphate H H H H SH triphosphate H H H H SMe triphosphate H H H HSEt triphosphate H H H H S-cyclopropyl triphosphate H H H H Ftriphosphate H H H H Cl triphosphate H H H H Br triphosphate H H H H Imonophosphate monophosphate monophosphate H H NH₂ monophosphatemonophosphate monophosphate H H NH-cyclopropyl monophosphatemonophosphate monophosphate H H OH monophosphate monophosphatemonophosphate H H F monophosphate monophosphate monophosphate H H Cldiphosphate diphosphate diphosphate H H NH₂ diphosphate diphosphatediphosphate H H NH-cyclopropyl diphosphate diphosphate diphosphate H HOH diphosphate diphosphate diphosphate H H F diphosphate diphosphatediphosphate H H Cl triphosphate triphosphate triphosphate H H NH₂triphosphate triphosphate triphosphate H H NH-cyclopropyl triphosphatetriphosphate triphosphate H H OH triphosphate triphosphate triphosphateH H F triphosphate triphosphate triphosphate H H Cl H H H F H NH₂ H H HF H NH-cyclopropyl H H H F H OH H H H F H F H H H F H Cl H H H Cl H NH₂H H H Cl H NH-cyclopropyl H H H Cl H OH H H H Cl H F H H H Cl H Cl H H HBr H NH₂ H H H Br H NH-cyclopropyl H H H Br H OH H H H Br H F H H H Br HCl H H H NH₂ H NH₂ H H H NH₂ H NH-cyclopropyl H H H NH₂ H OH H H H NH₂ HF H H H NH₂ H Cl H H H SH H NH₂ H H H SH H NH-cyclopropyl H H H SH H OHH H H SH H F H H H SH H Cl acetyl H H H H NH₂ acetyl H H H HNH-cyclopropyl acetyl H H H H OH acetyl H H H H F acetyl H H H H Clacetyl H H F H NH₂ acetyl H H F H NH-cyclopropyl acetyl H H F H OHacetyl H H F H F acetyl H H F H Cl H acetyl acetyl H H NH₂ H acetylacetyl H H NH-cyclopropyl H acetyl acetyl H H OH H acetyl acetyl H H F Hacetyl acetyl H H Cl acetyl acetyl acetyl H H NH₂ acetyl acetyl acetyl HH NH-cyclopropyl acetyl acetyl acetyl H H OH acetyl acetyl acetyl H H Facetyl acetyl acetyl H H Cl monophosphate acetyl acetyl H H NH₂monophosphate acetyl acetyl H H NH-cyclopropyl monophosphate acetylacetyl H H OH monophosphate acetyl acetyl H H F monophosphate acetylacetyl H H Cl diphosphate acetyl acetyl H H NH₂ diphosphate acetylacetyl H H NH-cyclopropyl diphosphate acetyl acetyl H H OH diphosphateacetyl acetyl H H F diphosphate acetyl acetyl H H Cl triphosphate acetylacetyl H H NH₂ triphosphate acetyl acetyl H H NH-cyclopropyltriphosphate acetyl acetyl H H OH triphosphate acetyl acetyl H H Ftriphosphate acetyl acetyl H H Cl H H H H NH₂ H H H H H NH₂ NH₂ H H H HNH₂ NH-cyclopropyl H H H H NH₂ NH-methyl H H H H NH₂ NH-ethyl H H H HNH₂ NH-acetyl H H H H NH₂ OH H H H H NH₂ OMe H H H H NH₂ OEt H H H H NH₂O-cyclopropyl H H H H NH₂ O-acetyl H H H H NH₂ SH H H H H NH₂ SMe H H HH NH₂ SEt H H H H NH₂ S-cyclopropyl H H H H NH₂ F H H H H NH₂ Cl H H H HNH₂ Br H H H H NH₂ I monophosphate H H H NH₂ NH₂ monophosphate H H H NH₂NH-acetyl monophosphate H H H NH₂ NH-cyclopropyl monophosphate H H H NH₂NH-methyl monophosphate H H H NH₂ NH-ethyl monophosphate H H H NH₂ OHmonophosphate H H H NH₂ O-acetyl monophosphate H H H NH₂ OMemonophosphate H H H NH₂ OEt monophosphate H H H NH₂ O-cyclopropylmonophosphate H H H NH₂ SH monophosphate H H H NH₂ SMe monophosphate H HH NH₂ SEt monophosphate H H H NH₂ S-cyclopropyl monophosphate H H H NH₂F monophosphate H H H NH₂ Cl monophosphate H H H NH₂ Br monophosphate HH H NH₂ I diphosphate H H H NH₂ NH₂ diphosphate H H H NH₂ NH-acetyldiphosphate H H H NH₂ NH-cyclopropyl diphosphate H H H NH₂ NH-methyldiphosphate H H H NH₂ NH-ethyl diphosphate H H H NH₂ OH diphosphate H HH NH₂ O-acetyl diphosphate H H H NH₂ OMe diphosphate H H H NH₂ OEtdiphosphate H H H NH₂ O-cyclopropyl diphosphate H H H NH₂ SH diphosphateH H H NH₂ SMe diphosphate H H H NH₂ SEt diphosphate H H H NH₂S-cyclopropyl diphosphate H H H NH₂ F diphosphate H H H NH₂ Cldiphosphate H H H NH₂ Br diphosphate H H H NH₂ I triphosphate H H H NH₂NH₂ triphosphate H H H NH₂ NH-acetyl triphosphate H H H NH₂NH-cyclopropyl triphosphate H H H NH₂ NH-methyl triphosphate H H H NH₂NH-ethyl triphosphate H H H NH₂ OH triphosphate H H H NH₂ OMetriphosphate H H H NH₂ OEt triphosphate H H H NH₂ O-cyclopropyltriphosphate H H H NH₂ O-acetyl triphosphate H H H NH₂ SH triphosphate HH H NH₂ SMe triphosphate H H H NH₂ SEt triphosphate H H H NH₂S-cyclopropyl triphosphate H H H NH₂ F triphosphate H H H NH₂ Cltriphosphate H H H NH₂ Br triphosphate H H H NH₂ I monophosphatemonophosphate monophosphate H NH₂ NH₂ monophosphate monophosphatemonophosphate H NH₂ NH-cyclopropyl monophosphate monophosphatemonophosphate H NH₂ OH monophosphate monophosphate monophosphate H NH₂ Fmonophosphate monophosphate monophosphate H NH₂ Cl diphosphatediphosphate diphosphate H NH₂ NH₂ diphosphate diphosphate diphosphate HNH₂ NH-cyclopropyl diphosphate diphosphate diphosphate H NH₂ OHdiphosphate diphosphate diphosphate H NH₂ F diphosphate diphosphatediphosphate H NH₂ Cl triphosphate triphosphate triphosphate H NH₂ NH₂triphosphate triphosphate triphosphate H NH₂ NH-cyclopropyl triphosphatetriphosphate triphosphate H NH₂ OH triphosphate triphosphatetriphosphate H NH₂ F triphosphate triphosphate triphosphate H NH₂ Cl H HH F NH₂ NH₂ H H H F NH₂ NH-cyclopropyl H H H F NH₂ OH H H H F NH₂ F H HH F NH₂ Cl H H H Cl NH₂ NH₂ H H H Cl NH₂ NH-cyclopropyl H H H Cl NH₂ OHH H H Cl NH₂ F H H H Cl NH₂ Cl H H H Br NH₂ NH₂ H H H Br NH₂NH-cyclopropyl H H H Br NH₂ OH H H H Br NH₂ F H H H Br NH₂ Cl H H H NH₂NH₂ NH₂ H H H NH₂ NH₂ NH-cyclopropyl H H H NH₂ NH₂ OH H H H NH₂ NH₂ F HH H NH₂ NH₂ Cl H H H SH NH₂ NH₂ H H H SH NH₂ NH-cyclopropyl H H H SH NH₂OH H H H SH NH₂ F H H H SH NH₂ Cl acetyl H H H NH₂ NH₂ acetyl H H H NH₂NH-cyclopropyl acetyl H H H NH₂ OH acetyl H H H NH₂ F acetyl H H H NH₂Cl acetyl H H F NH₂ NH₂ acetyl H H F NH₂ NH-cyclopropyl acetyl H H F NH₂OH acetyl H H F NH₂ F acetyl H H F NH₂ Cl H acetyl acetyl H NH₂ NH₂ Hacetyl acetyl H NH₂ NH-cyclopropyl H acetyl acetyl H NH₂ OH H acetylacetyl H NH₂ F H acetyl acetyl H NH₂ Cl acetyl acetyl acetyl H NH₂ NH₂acetyl acetyl acetyl H NH₂ NH-cyclopropyl acetyl acetyl acetyl H NH₂ OHacetyl acetyl acetyl H NH₂ F acetyl acetyl acetyl H NH₂ Cl monophosphateacetyl acetyl H NH₂ NH₂ monophosphate acetyl acetyl H NH₂ NH-cyclopropylmonophosphate acetyl acetyl H NH₂ OH monophosphate acetyl acetyl H NH₂ Fmonophosphate acetyl acetyl H NH₂ Cl diphosphate acetyl acetyl H NH₂ NH₂diphosphate acetyl acetyl H NH₂ NH-cyclopropyl diphosphate acetyl acetylH NH₂ OH diphosphate acetyl acetyl H NH₂ F diphosphate acetyl acetyl HNH₂ Cl triphosphate acetyl acetyl H NH₂ NH₂ triphosphate acetyl acetyl HNH₂ NH-cyclopropyl triphosphate acetyl acetyl H NH₂ OH triphosphateacetyl acetyl H NH₂ F triphosphate acetyl acetyl H NH₂ Cl H H H H Cl H HH H H Cl H H H H H Cl NH₂ H H H H Cl NH-cyclopropyl H H H H Cl NH-methylH H H H Cl NH-ethyl H H H H Cl NH-acetyl H H H H Cl OH H H H H Cl OMe HH H H Cl OEt H H H H Cl O-cyclopropyl H H H H Cl O-acetyl H H H H Cl SHH H H H Cl SMe H H H H Cl SEt H H H H Cl S-cyclopropyl monophosphate H HH Cl NH₂ monophosphate H H H Cl NH-acetyl monophosphate H H H ClNH-cyclopropyl monophosphate H H H Cl NH-methyl monophosphate H H H ClNH-ethyl monophosphate H H H Cl OH monophosphate H H H Cl O-acetylmonophosphate H H H Cl OMe monophosphate H H H Cl OEt monophosphate H HH Cl O-cyclopropyl monophosphate H H H Cl SH monophosphate H H H Cl SMemonophosphate H H H Cl SEt monophosphate H H H Cl S-cyclopropyldiphosphate H H H Cl NH₂ diphosphate H H H Cl NH-acetyl diphosphate H HH Cl NH-cyclopropyl diphosphate H H H Cl NH-methyl diphosphate H H H ClNH-ethyl diphosphate H H H Cl OH diphosphate H H H Cl O-acetyldiphosphate H H H Cl OMe diphosphate H H H Cl OEt diphosphate H H H ClO-cyclopropyl diphosphate H H H Cl SH diphosphate H H H Cl SMediphosphate H H H Cl SEt diphosphate H H H Cl S-cyclopropyl triphosphateH H H Cl NH₂ triphosphate H H H Cl NH-acetyl triphosphate H H H ClNH-cyclopropyl triphosphate H H H Cl NH-methyl triphosphate H H H ClNH-ethyl triphosphate H H H Cl OH triphosphate H H H Cl OMe triphosphateH H H Cl OEt triphosphate H H H Cl O-cyclopropyl triphosphate H H H ClO-acetyl triphosphate H H H Cl SH triphosphate H H H Cl SMe triphosphateH H H Cl SEt triphosphate H H H Cl S-cyclopropyl monophosphatemonophosphate monophosphate H Cl NH₂ monophosphate monophosphatemonophosphate H Cl NH-cyclopropyl monophosphate monophosphatemonophosphate H Cl OH diphosphate diphosphate diphosphate H Cl NH₂diphosphate diphosphate diphosphate H Cl NH-cyclopropyl diphosphatediphosphate diphosphate H Cl OH triphosphate triphosphate triphosphate HCl NH₂ triphosphate triphosphate triphosphate H Cl NH-cyclopropyltriphosphate triphosphate triphosphate H Cl OH H H H F Cl NH₂ H H H F ClNH-cyclopropyl H H H F Cl OH H H H Cl Cl NH₂ H H H Cl Cl NH-cyclopropylH H H Cl Cl OH H H H Br Cl NH₂ H H H Br Cl NH-cyclopropyl H H H Br Cl OHH H H NH₂ Cl NH₂ H H H NH₂ Cl NH-cyclopropyl H H H NH₂ Cl OH H H H SH ClNH₂ H H H SH Cl NH-cyclopropyl H H H SH Cl OH acetyl H H H Cl NH₂ acetylH H H Cl NH-cyclopropyl acetyl H H H Cl OH acetyl H H F Cl NH₂ acetyl HH F Cl NH-cyclopropyl acetyl H H F Cl OH H acetyl acetyl H Cl NH₂ Hacetyl acetyl H Cl NH-cyclopropyl H acetyl acetyl H Cl OH acetyl acetylacetyl H Cl NH₂ acetyl acetyl acetyl H Cl NH-cyclopropyl acetyl acetylacetyl H Cl OH monophosphate acetyl acetyl H Cl NH₂ monophosphate acetylacetyl H Cl NH-cyclopropyl monophosphate acetyl acetyl H Cl OHdiphosphate acetyl acetyl H Cl NH₂ diphosphate acetyl acetyl H ClNH-cyclopropyl diphosphate acetyl acetyl H Cl OH triphosphate acetylacetyl H Cl NH₂ triphosphate acetyl acetyl H Cl NH-cyclopropyltriphosphate acetyl acetyl H Cl OH H H H H Cl NH₂ H H H H ClNH-cyclopropyl H H H H Cl OH H H H H Br NH₂ H H H H Br NH-cyclopropyl HH H H Br OH

Alternatively, the following nucleosides of Formula V are prepared,using the appropriate sugar and pyrimidine or purine bases.

wherein: R¹ R² R³ X¹ Y H H H H H H H H H NH₂ H H H H NH-cyclopropyl H HH H NH-methyl H H H H NH-ethyl H H H H NH-acetyl H H H H OH H H H H OMeH H H H OEt H H H H O-cyclopropyl H H H H O-acetyl H H H H SH H H H HSMe H H H H SEt H H H H S-cyclopropyl monophosphate H H H NH₂monophosphate H H H NH-acetyl monophosphate H H H NH-cyclopropylmonophosphate H H H NH-methyl monophosphate H H H NH-ethyl monophosphateH H H OH monophosphate H H H O-acetyl monophosphate H H H OMemonophosphate H H H OEt monophosphate H H H O-cyclopropyl monophosphateH H H SH monophosphate H H H SMe monophosphate H H H SEt monophosphate HH H S-cyclopropyl diphosphate H H H NH₂ diphosphate H H H NH-acetyldiphosphate H H H NH-cyclopropyl diphosphate H H H NH-methyl diphosphateH H H NH-ethyl diphosphate H H H OH diphosphate H H H O-acetyldiphosphate H H H OMe diphosphate H H H OEt diphosphate H H HO-cyclopropyl diphosphate H H H SH diphosphate H H H SMe diphosphate H HH SEt diphosphate H H H S-cyclopropyl triphosphate H H H NH₂triphosphate H H H NH-acetyl triphosphate H H H NH-cyclopropyltriphosphate H H H NH-methyl triphosphate H H H NH-ethyl triphosphate HH H OH triphosphate H H H OMe triphosphate H H H OEt triphosphate H H HO-cyclopropyl triphosphate H H H O-acetyl triphosphate H H H SHtriphosphate H H H SMe triphosphate H H H SEt triphosphate H H HS-cyclopropyl monophosphate monophosphate monophosphate H NH₂monophosphate monophosphate monophosphate H NH-cyclopropyl monophosphatemonophosphate monophosphate H OH diphosphate diphosphate diphosphate HNH₂ diphosphate diphosphate diphosphate H NH-cyclopropyl diphosphatediphosphate diphosphate H OH triphosphate triphosphate triphosphate HNH₂ triphosphate triphosphate triphosphate H NH-cyclopropyl triphosphatetriphosphate triphosphate H OH H H H F NH₂ H H H F NH-cyclopropyl H H HF OH H H H Cl NH₂ H H H Cl NH-cyclopropyl H H H Cl OH H H H Br NH₂ H H HBr NH-cyclopropyl H H H Br OH H H H NH₂ NH₂ H H H NH₂ NH-cyclopropyl H HH NH₂ OH H H H SH NH₂ H H H SH NH-cyclopropyl H H H SH OH acetyl H H HNH₂ acetyl H H H NH-cyclopropyl acetyl H H H OH acetyl H H F NH₂ acetylH H F NH-cyclopropyl acetyl H H F OH H acetyl acetyl H NH₂ H acetylacetyl H NH-cyclopropyl H acetyl acetyl H OH acetyl acetyl acetyl H NH₂acetyl acetyl acetyl H NH-cyclopropyl acetyl acetyl acetyl H OHmonophosphate acetyl acetyl H NH₂ monophosphate acetyl acetyl HNH-cyclopropyl monophosphate acetyl acetyl H OH diphosphate acetylacetyl H NH₂ diphosphate acetyl acetyl H NH-cyclopropyl diphosphateacetyl acetyl H OH triphosphate acetyl acetyl H NH₂ triphosphate acetylacetyl H NH-cyclopropyl triphosphate acetyl acetyl H OH

Alternatively, the following nucleosides of Formula X are prepared,using the appropriate sugar and pyrimidine or purine bases.

wherein: R¹ R² R³ R⁶ X Base H H H CH₃ O 2,4-O- Diacetyluracil H H H CH₃O Hypoxanthine H H H CH₃ O 2,4-O- Diacetylthymine H H H CH₃ O Thymine HH H CH₃ O Gytosine H H H CH₃ O 4-(N-mono- acetyl)cytosine H H H CH₃ O4-(N,N- diacetyl)cytosine H H H CH₃ O Uracil H H H CH₃ O 5-FluorouracilH H H CH₃ S 2,4-O- Diacetyluraci H H H CH₃ S Hypoxanthine H H H CH₃ S2,4-O- Diacetylthymine H H H CH₃ S Thymine H H H CH₃ S Cytosine H H HCH₃ S 4-(N-mono- acetyl)cytosine H H H CH₃ S 4-(N,N- diacetyl)cytosine HH H CH₃ S Uracil H H H CH₃ S 5-Fluorouracil monophosphate H H CH₃ O2,4-O- Diacetyluracil monophosphate H H CH₃ O Hypoxanthine monophosphateH H CH₃ O 2,4-O- Diacetylthym monophosphate H H CH₃ O Thyminemonophosphate H H CH₃ O Cytosine monophosphate H H CH₃ O 4-(N-mono-acetyl)cytosine monophosphate H H CH₃ O 4-(N,N- diacetyl)cytosinemonophosphate H H CH₃ O Uracil monophosphate H H CH₃ O 5-Fluorouracilmonophosphate H H CH₃ S 2,4-O- Diacetyluracil monophosphate H H CH₃ SHypoxanthine monophosphate H H CH₃ S 2,4-O- Diacetylthym monophosphate HH CH₃ S Thymine monophosphate H H CH₃ S Cytosine monophosphate H H CH₃ S4-(N-mono- acetyl)cytosine monophosphate H H CH₃ S 4-(N,N-diacetyl)cytosine monophosphate H H CH₃ S Uracil monophosphate H H CH₃ S5-Fluorouracil diphosphate H H CH₃ O 2,4-O- Diacetyluracil diphosphate HH CH₃ O Hypoxanthine diphosphate H H CH₃ O 2,4-O- Diacetylthyminediphosphate H H CH₃ O Thymine diphosphate H H CH₃ O Cytosine diphosphateH H CH₃ O 4-(N-mono- acetyl)cytosine diphosphate H H CH₃ O 4-(N,N-diacetyl)cytosine diphosphate H H CH₃ O Uracil diphosphate H H CH₃ O5-Fluorouracil diphosphate H H CH₃ S 2,4-O- Diacetyluracil diphosphate HH CH₃ S Hypoxanthine diphosphate H H CH₃ S 2,4-O- Diacetylthymdiphosphate H H CH₃ S Thymine diphosphate H H CH₃ S Cytosinetriphosphate H H CH₃ O 2,4-O- Diacetyluracil triphosphate H H CH₃ OHypoxanthine triphosphate H H CH₃ O 2,4-O-Diacetylthymine triphosphate HH CH₃ O Thymine triphosphate H H CH₃ O Cytosine triphosphate H H CH₃ O4-(N-mono- acetyl)cytosine triphosphate H H CH₃ O 4-(N,N-diacetyl)cytosine triphosphate H H CH₃ O Uracil triphosphate H H CH₃ O5-Fluorouracil triphosphate H H CH₃ S 2,4-O- Diacetyluracil triphosphateH H CH₃ S Hypoxanthine triphosphate H H CH₃ S 2,4-O- Diacetylthyminetriphosphate H H CH₃ S Thymine triphosphate H H CH₃ S Cytosinemonophosphate monophosphate monophosphate CF₃ O 2,4-O- Diacetyluracilmonophosphate monophosphate monophosphate CF₃ O Hypoxanthinemonophosphate monophosphate monophosphate CF₃ O 2,4-O- Diacetylthyminemonophosphate monophosphate monophosphate CF₃ O Thymine monophosphatemonophosphate monophosphate CF₃ O Cytosine monophosphate monophosphatemonophosphate CF₃ O 4-(N-mono- acetyl)cytosine monophosphatemonophosphate monophosphate CF₃ O 4-(N,N- diacetyl)cytosinemonophosphate monophosphate monophosphate CF₃ O Uracil monophosphatemonophosphate monophosphate CF₃ O 5-Fluorouracil monophosphatemonophosphate monophosphate CF₃ S 2,4-O- Diacetyluracil monophosphatemonophosphate monophosphate CF₃ S Hypoxanthine monophosphatemonophosphate monophosphate CF₃ S 2,4-O- Diacetylthymine monophosphatemonophosphate monophosphate CF₃ S Thymine monophosphate monophosphatemonophosphate CF₃ S Cytosine monophosphate monophosphate monophosphateCF₃ S 4-(N-mono- acetyl)cytosine monophosphate monophosphatemonophosphate CF₃ S 4-(N,N- diacetyl)cytosine monophosphatemonophosphate monophosphate CF₃ S Uracil monophosphate monophosphatemonophosphate CF₃ S 5-Fluorouracil acetyl acetyl acetyl CF₃ O 4-(N,N-diacetyl)cytosine acetyl acetyl acetyl CF₃ S 4-(N,N- diacetyl)cytosineacetyl acetyl acetyl 2-bromo- O 4-(N,N- vinyl diacetyl)cytosine acetylacetyl acetyl 2-bromo- S 4-(N,N- vinyl diacetyl)cytosine H H H CH₃ O2-(N,N-diacetyl)- guanine H H H CH₃ O 6-O-acetyl guanine H H H CH₃ O8-fluoroguanine H H H CH₃ O guanine H H H CH₃ O 6-(N,N-diacetyl)-adenine H H H CH₃ O 2-fluoroadenine H H H CH₃ O 8-fluoroadenine H H HCH₃ O 2,8-difluoro- adenine H H H CH₃ O adenine H H H CH₃ S2-(N,N-diacetyl)- guanine H H H CH₃ S 6-O-acetyl guanine H H H CH₃ S8-fluoroguanine H H H CH₃ S guanine H H H CH₃ S 6-(N,N-diacetyl)-adenine H H H CH₃ S 2-fluoroadenine H H H CH₃ S 8-fluoroadenine H H HCH₃ S 2,8-difluoro- adenine H H H CH₃ S adenine monophosphate H H CH₃ O2-(N,N-diacetyl)- guanine monophosphate H H CH₃ O 6-O-acetyl guaninemonophosphate H H CH₃ O 8-fluoroguanine monophosphate H H CH₃ O guaninemonophosphate H H CH₃ O 6-(N,N-diacetyl)- adenine monophosphate H H CH₃O 2-fluoroadenine monophosphate H H CH₃ O 8-fluoroadenine monophosphateH H CH₃ O 2,8-difluoro- adenine monophosphate H H CH₃ O adeninemonophosphate H H CH₃ S 2-(N,N-diacetyl)- guanine monophosphate H H CH₃S 6-O-acetyl guanine monophosphate H H CH₃ S 8-fluoroguaninemonophosphate H H CH₃ S guanine monophosphate H H CH₃ S6-(N,N-diacetyl)- adenine monophosphate H H CH₃ S 2-fluoroadeninemonophosphate H H CH₃ S 8-fluoroadenine monophosphate H H CH₃ S2,8-difluoro- adenine monophosphate H H CH₃ S adenine diphosphate H HCH₃ O 2-(N,N-diacetyl)- guanine diphosphate H H CH₃ O 6-O-acetyl guaninediphosphate H H CH₃ O 8-fluoroguanine diphosphate H H CH₃ O guaninediphosphate H H CH₃ O 6-(N,N-diacetyl)- adenine diphosphate H H CH₃ O2-fluoroadenine diphosphate H H CH₃ O 8-fluoroadenine diphosphate H HCH₃ O 2,8-difluoro- adenine diphosphate H H CH₃ O adenine diphosphate HH CH₃ S 2-(N,N-diacetyl)- guanine diphosphate H H CH₃ S 6-O-acetylguanine diphosphate H H CH₃ S 8-fluoroguanine diphosphate H H CH₃ Sguanine diphosphate H H CH₃ S 6-(N,N-diacetyl)- adenine diphosphate H HCH₃ S 2-fluoroadenine diphosphate H H CH₃ S 8-fluoroadenine diphosphateH H CH₃ S 2,8-difluoro- adenine diphosphate H H CH₃ S adeninetriphosphate H H CH₃ O 2-(N,N-diacetyl)- guanine triphosphate H H CH₃ O6-O-acetyl guanine triphosphate H H CH₃ O 8-fluoroguanine triphosphate HH CH₃ O guanine triphosphate H H CH₃ O 6-(N,N-diacetyl)- adeninetriphosphate H H CH₃ O 2-fluoroadenine triphosphate H H CH₃ O8-fluoroadenine triphosphate H H CH₃ O 2,8-difluoro- adeninetriphosphate H H CH₃ O 2-(N,N-diacetyl)- guanine triphosphate H H CH₃ S6-O-acetyl guanine triphosphate H H CH₃ S 8-fluoroguanine triphosphate HH CH₃ S guanine triphosphate H H CH₃ S 6-(N,N-diacetyl)- adeninetriphosphate H H CH₃ S 2-fluoroadenine triphosphate H H CH₃ S8-fluoroadenine triphosphate H H CH₃ S 2,8-difluoro- adeninetriphosphate H H CH₃ S adenine monophosphate monophosphate monophosphateCF₃ O 2-(N,N-diacetyl)- guanine monophosphate monophosphatemonophosphate CF₃ O 6-O-acetyl guanine monophosphate monophosphatemonophosphate CF₃ O 8-fluoroguanine monophosphate monophosphatemonophosphate CF₃ O guanine monophosphate monophosphate monophosphateCF₃ O 6-(N,N-diacetyl)- adenine monophosphate monophosphatemonophosphate CF₃ O 2-fluoroadenine monophosphate monophosphatemonophosphate CF₃ O 8-fluoroadenine monophosphate monophosphatemonophosphate CF₃ O 2,8-difluoro- adenine monophosphate monophosphatemonophosphate CF₃ O adenine monophosphate monophosphate monophosphateCF₃ S 2-(N,N-diacetyl)- guanine monophosphate monophosphatemonophosphate CF₃ S 6-O-acetyl guanine monophosphate monophosphatemonophosphate CF₃ S 8-fluoroguanine monophosphate monophosphatemonophosphate CF₃ S guanine monophosphate monophosphate monophosphateCF₃ S 6-(N,N-diacetyl)- adenine monophosphate monophosphatemonophosphate CF₃ S 2-fluoroadenine monophosphate monophosphatemonophosphate CF₃ S 8-fluoroadenine monophosphate monophosphatemonophosphate CF₃ S 2,8-difluoro- adenine monophosphate monophosphatemonophosphate CF₃ S adenine acetyl acetyl acetyl CF₃ O guanine acetylacetyl acetyl CF₃ S guanine acetyl acetyl acetyl 2-bromo- O guaninevinyl acetyl acetyl acetyl 2-bromo- S guanine vinyl

Alternatively, the following nucleosides of Formula XI are prepared,using the appropriate sugar and pyrimidine or purine bases.

wherein: R¹ R² R⁷ R⁶ X Base H H H CH₃ O 2,4-O-Diacetyluracil H H H CH₃ OHypoxanthine H H H CH₃ O 2,4-O-Diacetylthymine H H H CH₃ O Thymine H H HCH₃ O Cytosine H H H CH₃ O 4-(N-mono- acetyl)cytosine H H H CH₃ O4-(N,N-diacetyl)cytosine H H H CH₃ O Uracil H H H CH₃ O 5-Fluorouracil HH H CH₃ S 2,4-O-Diacetyluracil H H H CH₃ S Hypoxanthine H H H CH₃ S2,4-O-Diacetylthymine H H H CH₃ S Thymine H H H CH₃ S Cytosine H H H CH₃S 4-(N-mono-acetyl)cytosin H H H CH₃ S 4-(N,N-diacetyl)cytosine H H HCH₃ S Uracil H H H CH₃ S 5-Fluorouracil CH₃ monophosphate H H CH₃ O2,4-O-Diacetyluracil monophosphate H H CH₃ O Hypoxanthine monophosphateH H CH₃ O 2,4-O-Diacetylthymine monophosphate H H CH₃ O Thyminemonophosphate H H CH₃ O Cytosine monophosphate H H CH₃ O 4-(N-mono-acetyl)cytosine monophosphate H H CH₃ O 4-(N,N-diacetyl)cytosinemonophosphate H H CH₃ O Uracil monophosphate H H CH₃ O 5-Fluorouracilmonophosphate H H CH₃ S 2,4-O-Diacetyluracil monophosphate H H CH₃ SHypoxanthine monophosphate H H CH₃ S 2,4-O-Diacetylthymine monophosphateH H CH₃ S Thymine monophosphate H H CH₃ S Cytosine monophosphate H H CH₃S 4-(N-mono- acetyl)cytosine monophosphate H H CH₃ S4-(N,N-diacetyl)cytosine monophosphate H H CH₃ S Uracil monophosphate HH CH₃ S 5-Fluorouracil diphosphate H H CH₃ O 2,4-O-Diacetyluracdiphosphate H H CH₃ O Hypoxanthine diphosphate H H CH₃ O2,4-O-Diacetylthymine diphosphate H H CH₃ O Thymine diphosphate H H CH₃O Cytosine diphosphate H H CH₃ O 4-(N-mono- acetyl)cytosine diphosphateH H CH₃ O 4-(N,N-diacetyl)cytosine diphosphate H H CH₃ O Uracildiphosphate H H CH₃ O 5-Fluorouracil diphosphate H H CH₃ S2,4-O-Diacetyluracil diphosphate H H CH₃ S Hypoxanthine diphosphate H HCH₃ S 2,4-O-Diacetylthym diphosphate H H CH₃ S Thymine diphosphate H HCH₃ S Cytosine triphosphate H H CH₃ O 2,4-O-Diacetyluracil triphosphateH H CH₃ O Hypoxanthine triphosphate H H CH₃ O 2,4-O-Diacetylthyminetriphosphate H H CH₃ O Thymine triphosphate H H CH₃ O Cytosinetriphosphate H H CH₃ O 4-(N-mono- acetyl)cytosine triphosphate H H CH₃ O4-(N,N-diacetyl)cytos triphosphate H H CH₃ O Uracil triphosphate H H CH₃O 5-Fluorouracil triphosphate H H CH₃ S 2,4-O-Diacetyluraciltriphosphate H H CH₃ S Hypoxanthine triphosphate H H CH₃ S2,4-O-Diacetylthym triphosphate H H CH₃ S Thymine triphosphate H H CH₃ SCytosine monophosphate monophosphate Br CF₃ O 2,4-O-Diacetyluracilmonophosphate monophosphate Br CF₃ O Hypoxanthine monophosphatemonophosphate Br CF₃ O 2,4-O-Diacetylthymine monophosphate monophosphateBr CF₃ O Thymine monophosphate monophosphate Br CF₃ O Cytosinemonophosphate monophosphate Br CF₃ O 4-(N-mono- acetyl)cytosinemonophosphate monophosphate Br CF₃ O 4-(N,N-diacetyl)cytosinemonophosphate monophosphate Br CF₃ O Uracil monophosphate monophosphateBr CF₃ O 5-Fluorouracil monophosphate monophosphate Br CF₃ S2,4-O-Diacetyluracil monophosphate monophosphate Br CF₃ S Hypoxanthinemonophosphate monophosphate Br CF₃ S 2,4-O-Diacetylthymine monophosphatemonophosphate Br CF₃ S Thymine monophosphate monophosphate Br CF₃ SCytosine monophosphate monophosphate Br CF₃ S 4-(N-mono- acetyl)cytosinemonophosphate monophosphate Br CF₃ S 4-(N,N-diacetyl)cytos monophosphatemonophosphate Br CF₃ S Uracil monophosphate monophosphate Br CF₃ S5-Fluofouracil acetyl acetyl NO2 CF₃ O 4-(N,N-diacetyl)cytosine acetylacetyl NO2 CF₃ S 4-(N,N-diacetyl)cytosine acetyl acetyl NO2 CF₃ O4-(N,N-diacetyl)cytosine acetyl acetyl NO2 2-bromo- S4-(N,N-diacetyl)cytosine vinyl

Alternatively, the following nucleosides of Formula XII are prepared,using the appropriate sugar and pyrimidine or purine bases.

wherein: R¹ R⁶ X Base H CH₃ O 2,4-O-Diacetyluracil H CH₃ O HypoxanthineH CH₃ O 2,4-O-Diacetylthymine H CH₃ O Thymine H CH₃ O Cytosine H CH₃ O4-(N-mono-acetyl)cytosine H CH₃ O 4-(N,N-diacetyl)cytosine H CH₃ OUracil H CH₃ O 5-Fluorouracil H CH₃ S 2,4-O-Diacetyluracil H CH₃ SHypoxanthine H CH₃ S 2,4-O-Diacetylthymine H CH₃ S Thymine H CH₃ SCytosine H CH₃ S 4-(N-mono-acetyl)cytosine H CH₃ S4-(N,N-diacetyl)cytosine H CH₃ S Uracil H CH₃ S 5-Fluorouracilmonophosphate CH₃ O 2,4-O-Diacetyluracil monophosphate CH₃ OHypoxanthine monophosphate CH₃ O 2,4-O-Diacetylthymine monophosphate CH₃O Thymine monophosphate CH₃ O Cytosine monophosphate CH₃ O4-(N-mono-acetyl)cytosine monophosphate CH₃ O 4-(N,N-diacetyl)cytosinemonophosphate CH₃ O Uracil monophosphate CH₃ O 5-Fluorouracilmonophosphate CH₃ S 2,4-O-Diacetyluracil monophosphate CH₃ SHypoxanthine monophosphate CH₃ S 2,4-O-Diacetylthymine monophosphate CH₃S Thymine monophosphate CH₃ S Cytosine monophosphate CH₃ S4-(N-mono-acetyl)cytosine monophosphate CH₃ S 4-(N,N-diacetyl)cytosinemonophosphate CH₃ S Uracil monophosphate CH₃ S 5-Fluorouracildiphosphate 2H₃ O 2,4-O-Diacetyluracil diphosphate CH₃ O Hypoxanthinediphosphate CH₃ O 2,4-O-Diacetylthymine diphosphate CH₃ O Thyminediphosphate CH₃ O Cytosine diphosphate CH₃ O 4-(N-mono-acetyl)cytosinediphosphate CH₃ O 4-(N,N-diacetyl)cytosine diphosphate CH₃ O Uracildiphosphate CH₃ O 5-Fluorouracil diphosphate CH₃ S 2,4-O-Diacetyluracildiphosphate CH₃ S Hypoxanthine diphosphate CH₃ S 2,4-O-Diacetylthyminediphosphate CH₃ S Thymine diphosphate CH₃ S Cytosine triphosphate CH₃ O2,4-O-Diacetyluracil triphosphate CH₃ O Hypoxanthine triphosphate CH₃ O2,4-O-Diacetylthymine triphosphate CH₃ O Thymine triphosphate CH₃ OCytosine triphosphate CH₃ O 4-(N-mono-acetyl)cytosine triphosphate CH₃ O4-(N,N-diacetyl)cytosine triphosphate CH₃ O Uracil triphosphate CH₃ O5-Fluorouracil triphosphate CH₃ S 2,4-O-Diacetyluracil triphosphate CH₃S Hypoxanthine triphosphate CH₃ S 2,4-O-Diacetylthymine triphosphate CH₃S Thymine triphosphate CH₃ S Cytosine monophosphate CF₃ O2,4-O-Diacetyluracil monophosphate CF₃ O Hypoxanthine monophosphate CF₃O 2,4-O-Diacetylthymine monophosphate CF₃ O Thymine monophosphate CF₃ OCytosine monophosphate CF₃ O 4-(N-mono-acetyl)cytosine monophosphate CF₃O 4-(N,N-diacetyl)cytosine monophosphate CF₃ O Uracil monophosphate CF₃O 5-Fluorouracil monophosphate CF₃ S 2,4-O-Diacetyluracil monophosphateCF₃ S Hypoxanthine monophosphate CF₃ S 2,4-O-Diacetylthyminemonophosphate CF₃ S Thymine monophosphate CF₃ S Cytosine monophosphateCF₃ S 4-(N-mono-acetyl)cytosine monophosphate CF₃ S4-(N,N-diacetyl)cytosine monophosphate CF₃ S Uracil monophosphate CF₃ S5-Fluorouracil acetyl CF₃ O 4-(N,N-diacetyl)cytosine acetyl CF₃ S4-(N,N-diacetyl)cytosine acetyl 2-bromo-vinyl O 4-(N,N-diacetyl)cytosineacetyl 2-bromo-vinyl S 4-(N,N-diacetyl)cytosine

Alternatively, the following nucleosides of Formula XVII are prepared,using the appropriate sugar and pyrimidine or purine bases.

wherein: R¹ R⁶ R⁷ X Base R⁹ R¹⁰ H CH₃ H O 2,4-O-Diacetyluracil NHAc Me HCH₃ H O Hypoxanthine NH2 Me H CH₃ H O 2,4-O-Diacetylthymine NHAc Me HCH₃ H O Thymine NH2 Me H CH₃ H O Cytosine NH2 Me H CH₃ H O4-(N-mono-acetyl)cytosine NHAc Me H CH₃ H O 4-(N,N-diacetyl)cytosineNHAc Me H CH₃ H O Uracil NH2 Me H CH₃ H O 5-Fluorouracil NH2 Me H CH₃ HS 2,4-O-Diacetyluracil NHAc Me H CH₃ H S Hypoxanthine NH2 Me H CH₃ H S2,4-O-Diacetylthymine NHAc Me H CH₃ H S Thymine NH2 Me H CH₃ H SCytosine NH2 Me H CH₃ H S 4-(N-mono-acetyl)cytosine NHAc Me H CH₃ H S4-(N,N-diacetyl)cytosine NHAc Me H CH₃ H S Uracil NH2 Me H CH₃ H S5-Fluorouracil NH2 Me monophosphate CH₃ H O 2,4-O-Diacetyluracil NHAc Memonophosphate CH₃ H O Hypoxanthine NH2 Me monophosphate CH₃ H O2,4-O-Diacetylthymine NHAc Me monophosphate CH₃ H O Thymine NH2 Memonophosphate CH₃ H O Cytosine NH2 Me monophosphate CH₃ H O4-(N-mono-acetyl)cytosine NHAC Me monophosphate CH₃ H O4-(N,N-diacetyl)cytosine NHAc Me monophosphate CH₃ H O Uracil NH2 Memonophosphate CH₃ H O 5-Fluorouracil NH2 Me monophosphate CH₃ H S2,4-O-Diacetyluracil NHAc Me monophosphate CH₃ H S Hypoxanthine NH2 Memonophosphate CH₃ H S 2,4-O-Diacetylthymine NHAc Me monophosphate CH₃ HS Thymine NH2 Me monophosphate CH₃ H S Cytosine NH2 Me monophosphate CH₃H S 4-(N-mono-acetyl)cytosine NHAc Me monophosphate CH₃ H S4-(N,N-diacetyl)cytosine NHAc Me monophosphate CH₃ H S Uracil NH2 Memonophosphate CH₃ H S 5-Fluorouracil NH2 Me diphosphate CH₃ H O2,4-O-Diacetyluracil NHAc Me diphosphate CH₃ H O Hypoxanthine NH2 Mediphosphate CH₃ H O 2,4-O-Diacetylthymine NH2 Me diphosphate CH₃ H OThymine NH2 Me diphosphate CH₃ H O Cytosine NH2 Me diphosphate CH₃ H O4-(N-mono-acetyl)cytosine NHAc Me diphosphate CH₃ H O4-(N,N-diacetyl)cytos NHAc Me diphosphate CH₃ H O Uracil NH2 Mediphosphate CH₃ H O 5-Fluorouracil NH2 Me diphosphate CH₃ H S2,4-O-Diacetyluracil NH2 Me diphosphate CH₃ H S Hypoxanthine NH2 Mediphosphate CH₃ H S 2,4-O-Diacetylthymine NHAc Me diphosphate CH₃ H SThymine NH2 Me diphosphate CH₃ H S Cytosine NH2 Me triphosphate CH₃ H O2,4-O-Diacetyluracil NHAc Me triphosphate CH₃ H O Hypoxanthine NHAc Metriphosphate CH₃ H O 2,4-O-Diacetylthymine NHAc Me triphosphate CH₃ H OThymine NH2 Me triphosphate CH₃ H O Cytosine NH2 Me triphosphate CH₃ H O4-(N-mono-acetyl)cytosine NHAc Me triphosphate CH₃ H O4-(N,N-diacetyl)cytosine NH2 Me triphosphate CH₃ H O Uracil NH2 Metriphosphate CH₃ H O 5-Fluorouracil NH2 Me triphosphate CH₃ H S2,4-O-Diacetyluracil NH2 Me triphosphate CH₃ H S Hypoxanthine NH2 Metriphosphate CH₃ H S 2,4-O-Diacetylthymine NH2 Me triphosphate CH₃ H SThymine NH2 Me triphosphate CH₃ H S Cytosine NH2 Me monophosphate CF₃ HO 2,4-O-Diacetyluracil NH2 Me monophosphate CF₃ H O Hypoxanthine NH2 Memonophosphate CF₃ H O 2,4-O-Diacetylthymine NH2 Me monophosphate CF₃ H OThymine NH2 Me monophosphate CF₃ H O Cytosine NH2 Me monophosphate CF₃ HO 4-(N-mono-acetyl)cytosine NH2 Me monophosphate CF₃ H O4-(N,N-diacetyl)cytosine NH2 Me monophosphate CF₃ H O Uracil NH2 Memonophosphate CF₃ H O 5-Fluorouracil NH2 Me monophosphate CF₃ H S2,4-O-Diacetyluracil NH2 Me monophosphate CF₃ H S Hypoxanthine NH2 Memonophosphate CF₃ H S 2,4-O-Diacetylthymine NH2 Me monophosphate CF₃ H SThymine NH2 Me monophosphate CF₃ H S Cytosine NH2 Me monophosphate CF₃ HS 4-(N-mono-acetyl)cytosine NH2 Me monophosphate CF₃ H S4-(N,N-diacetyl)cytosine NH2 Me monophosphate CF₃ H S Uracil NH2 Memonophosphate CF₃ H S 5-Fluorouracil NH2 Me acetyl CH₃ H O4-(N,N-diacetyl)cytosine H Br acetyl CH₃ H S 4-(N,N-diacetyl)cytosine HBr acetyl CH₃ OH O 4-(N,N-diacetyl)cytosine H Br acetyl CH₃ OH S4-(N,N-diacetyl)cytosine H Br

Example 3 Preparation of 3′-C-methylriboadenine

The title compound can be prepared according to a published procedure(R. F. Nutt, M. J. Dickinson, F. W. Holly, and E. Walton,“Branched-chain sugar nucleosides. III. 3′-C-methyladenine ”, J. Org.Chem. 1968, 33, 1789-1795) (Scheme 9).

In a similar manner, but using the appropriate sugar and pyrimidine orpurine bases, the following nucleosides of Formula III are prepared.

wherein: R¹ R² R³ X¹ X² Y H H H H H H H H H H H NH₂ H H H H HNH-cyclopropyl H H H H H NH-methyl H H H H H NH-ethyl H H H H HNH-acetyl H H H H H OH H H H H H OMe H H H H H OEt H H H H HO-cyclopropyl H H H H H O-acetyl H H H H H SH H H H H H SMe H H H H HSEt H H H H H S-cyclopropyl H H H H H F H H H H H Cl H H H H H Br H H HH H I monophosphate H H H H NH₂ monophosphate H H H H NH-acetylmonophosphate H H H H NH-cyclopropyl monophosphate H H H H NH-methylmonophosphate H H H H NH-ethyl monophosphate H H H H OH monophosphate HH H H O-acetyl monophosphate H H H H OMe monophosphate H H H H OEtmonophosphate H H H H O-cyclopropyl monophosphate H H H H SHmonophosphate H H H H SMe monophosphate H H H H SEt monophosphate H H HH S-cyclopropyl monophosphate H H H H F monophosphate H H H H Clmonophosphate H H H H Br monophosphate H H H H I diphosphate H H H H NH₂diphosphate H H H H NH-acetyl diphosphate H H H H NH-cyclopropyldiphosphate H H H H NH-methyl diphosphate H H H H NH-ethyl diphosphate HH H H OH diphosphate H H H H O-acetyl diphosphate H H H H OMediphosphate H H H H OEt diphosphate H H H H O-cyclopropyl diphosphate HH H H SH diphosphate H H H H SMe diphosphate H H H H SEt diphosphate H HH H S-cyclopropyl diphosphate H H H H F diphosphate H H H H Cldiphosphate H H H H Br diphosphate H H H H I triphosphate H H H H NH₂triphosphate H H H H NH-acetyl triphosphate H H H H NH-cyclopropyltriphosphate H H H H NH-methyl triphosphate H H H H NH-ethyltriphosphate H H H H OH triphosphate H H H H OMe triphosphate H H H HOEt triphosphate H H H H O-cyclopropyl triphosphate H H H H O-acetyltriphosphate H H H H SH triphosphate H H H H SMe triphosphate H H H HSEt triphosphate H H H H S-cyclopropyl triphosphate H H H H Ftriphosphate H H H H Cl triphosphate H H H H Br triphosphate H H H H Imonophosphate monophosphate monophosphate H H NH₂ monophosphatemonophosphate monophosphate H H NH-cyclopropyl monophosphatemonophosphate monophosphate H H OH monophosphate monophosphatemonophosphate H H F monophosphate monophosphate monophosphate H H Cldiphosphate diphosphate diphosphate H H NH₂ diphosphate diphosphatediphosphate H H NH-cyclopropyl diphosphate diphosphate diphosphate H HOH diphosphate diphosphate diphosphate H H F diphosphate diphosphatediphosphate H H Cl triphosphate triphosphate triphosphate H H NH₂triphosphate triphosphate triphosphate H H NH-cyclopropyl triphosphatetriphosphate triphosphate H H OH triphosphate triphosphate triphosphateH H F triphosphate triphosphate triphosphate H H Cl H H H F H NH₂ H H HF H NH-cyclopropyl H H H F H OH H H H F H F H H H F H Cl H H H Cl H NH₂H H H Cl H NH-cyclopropyl H H H Cl H OH H H H Cl H F H H H Cl H Cl H H HBr H NH₂ H H H Br H NH-cyclopropyl H H H Br H OH H H H Br H F H H H Br HCl H H H NH₂ H NH₂ H H H NH₂ H NH-cyclopropyl H H H NH₂ H OH H H H NH₂ HF H H H NH₂ H Cl H H H SH H NH₂ H H H SH H NH-cyclopropyl H H H SH H OHH H H SH H F H H H SH H Cl acetyl H H H H NH₂ acetyl H H H HNH-cyclopropyl acetyl H H H H OH acetyl H H H H F acetyl H H H H Clacetyl H H F H NH₂ acetyl H H F H NH-cyclopropyl acetyl H H F H OHacetyl H H F H F acetyl H H F H Cl H acetyl acetyl H H NH₂ H acetylacetyl H H NH-cyclopropyl H acetyl acetyl H H OH H acetyl acetyl H H F Hacetyl acetyl H H Cl acetyl acetyl acetyl H H NH₂ acetyl acetyl acetyl HH NH-cyclopropyl acetyl acetyl acetyl H H OH acetyl acetyl acetyl H H Facetyl acetyl acetyl H H Cl monophosphate acetyl acetyl H H NH₂monophosphate acetyl acetyl H H NH-cyclopropyl monophosphate acetylacetyl H H OH monophosphate acetyl acetyl H H F monophosphate acetylacetyl H H Cl diphosphate acetyl acetyl H H NH₂ diphosphate acetylacetyl H H NH-cyclopropyl diphosphate acetyl acetyl H H OH diphosphateacetyl acetyl H H F diphosphate acetyl acetyl H H Cl triphosphate acetylacetyl H H NH₂ triphosphate acetyl acetyl H H NH-cyclopropyltriphosphate acetyl acetyl H H OH triphosphate acetyl acetyl H H Ftriphosphate acetyl acetyl H H Cl H H H H NH₂ H H H H H NH₂ NH₂ H H H HNH₂ NH-cyclopropyl H H H H NH₂ NH-methyl H H H H NH₂ NH-ethyl H H H HNH₂ NH-acetyl H H H H NH₂ OH H H H H NH₂ OMe H H H H NH₂ OEt H H H H NH₂O-cyclopropyl H H H H NH₂ O-acetyl H H H H NH₂ SH H H H H NH₂ SMe H H HH NH₂ SEt H H H H NH₂ S-cyclopropyl H H H H NH₂ F H H H H NH₂ Cl H H H HNH₂ Br H H H H NH₂ I monophosphate H H H NH₂ NH₂ monophosphate H H H NH₂NH-acetyl monophosphate H H H NH₂ NH-cyclopropyl monophosphate H H H NH₂NH-methyl monophosphate H H H NH₂ NH-ethyl monophosphate H H H NH₂ OHmonophosphate H H H NH₂ O-acetyl monophosphate H H H NH₂ OMemonophosphate H H H NH₂ OEt monophosphate H H H NH₂ O-cyclopropylmonophosphate H H H NH₂ SH monophosphate H H H NH₂ SMe monophosphate H HH NH₂ SEt monophosphate H H H NH₂ S-cyclopropyl monophosphate H H H NH₂F monophosphate H H H NH₂ Cl monophosphate H H H NH₂ Br monophosphate HH H NH₂ I diphosphate H H H NH₂ NH₂ diphosphate H H H NH₂ NH-acetyldiphosphate H H H NH₂ NH-cyclopropyl diphosphate H H H NH₂ NH-methyldiphosphate H H H NH₂ NH-ethyl diphosphate H H H NH₂ OH diphosphate H HH NH₂ O-acetyl diphosphate H H H NH₂ OMe diphosphate H H H NH₂ OEtdiphosphate H H H NH₂ O-cyclopropyl diphosphate H H H NH₂ SH diphosphateH H H NH₂ SMe diphosphate H H H NH₂ SEt diphosphate H H H NH₂S-cyclopropyl diphosphate H H H NH₂ F diphosphate H H H NH₂ Cldiphosphate H H H NH₂ Br diphosphate H H H NH₂ I triphosphate H H H NH₂NH₂ triphosphate H H H NH₂ NH-acetyl triphosphate H H H NH₂NH-cyclopropyl triphosphate H H H NH₂ NH-methyl triphosphate H H H NH₂NH-ethyl triphosphate H H H NH₂ OH triphosphate H H H NH₂ OMetriphosphate H H H NH₂ OEt triphosphate H H H NH₂ O-cyclopropyltriphosphate H H H NH₂ O-acetyl triphosphate H H H NH₂ SH triphosphate HH H NH₂ SMe triphosphate H H H NH₂ SEt triphosphate H H H NH₂S-cyclopropyl triphosphate H H H NH₂ F triphosphate H H H NH₂ Cltriphosphate H H H NH₂ Br triphosphate H H H NH₂ I monophosphatemonophosphate monophosphate H NH₂ NH₂ monophosphate monophosphatemonophosphate H NH₂ NH-cyclopropyl monophosphate monophosphatemonophosphate H NH₂ OH monophosphate monophosphate monophosphate H NH₂ Fmonophosphate monophosphate monophosphate H NH₂ Cl diphosphatediphosphate diphosphate H NH₂ NH₂ diphosphate diphosphate diphosphate HNH₂ NH-cyclopropyl diphosphate diphosphate diphosphate H NH₂ OHdiphosphate diphosphate diphosphate H NH₂ F diphosphate diphosphatediphosphate H NH₂ Cl triphosphate triphosphate triphosphate H NH₂ NH₂triphosphate triphosphate triphosphate H NH₂ NH-cyclopropyl triphosphatetriphosphate triphosphate H NH₂ OH triphosphate triphosphatetriphosphate H NH₂ F triphosphate triphosphate triphosphate H NH₂ Cl H HH F NH₂ NH₂ H H H F NH₂ NH-cyclopropyl H H H F NH₂ OH H H H F NH₂ F H HH F NH₂ Cl H H H Cl NH₂ NH₂ H H H Cl NH₂ NH-cyclopropyl H H H Cl NH₂ OHH H H Cl NH₂ F H H H Cl NH₂ Cl H H H Br NH₂ NH₂ H H H Br NH₂NH-cyclopropyl H H H Br NH₂ OH H H H Br NH₂ F H H H Br NH₂ Cl H H H NH₂NH₂ NH₂ H H H NH₂ NH₂ NH-cyclopropyl H H H NH₂ NH₂ OH H H H NH₂ NH₂ F HH H NH₂ NH₂ Cl H H H SH NH₂ NH₂ H H H SH NH₂ NH-cyclopropyl H H H SH NH₂OH H H H SH NH₂ F H H H SH NH₂ Cl acetyl H H H NH₂ NH₂ acetyl H H H NH₂NH-cyclopropyl acetyl H H H NH₂ OH acetyl H H H NH₂ F acetyl H H H NH₂Cl acetyl H H F NH₂ NH₂ acetyl H H F NH₂ NH-cyclopropyl acetyl H H F NH₂OH acetyl H H F NH₂ F acetyl H H F NH₂ Cl H acetyl acetyl H NH₂ NH₂ Hacetyl acetyl H NH₂ NH-cyclopropyl H acetyl acetyl H NH₂ OH H acetylacetyl H NH₂ F H acetyl acetyl H NH₂ Cl acetyl acetyl acetyl H NH₂ NH₂acetyl acetyl acetyl H NH₂ NH-cyclopropyl acetyl acetyl acetyl H NH₂ OHacetyl acetyl acetyl H NH₂ F acetyl acetyl acetyl H NH₂ Cl monophosphateacetyl acetyl H NH₂ NH₂ monophosphate acetyl acetyl H NH₂ NH-cyclopropylmonophosphate acetyl acetyl H NH₂ OH monophosphate acetyl acetyl H NH₂ Fmonophosphate acetyl acetyl H NH₂ Cl diphosphate acetyl acetyl H NH₂ NH₂diphosphate acetyl acetyl H NH₂ NH-cyclopropyl diphosphate acetyl acetylH NH₂ OH diphosphate acetyl acetyl H NH₂ F diphosphate acetyl acetyl HNH₂ Cl triphosphate acetyl acetyl H NH₂ NH₂ triphosphate acetyl acetyl HNH₂ NH-cyclopropyl triphosphate acetyl acetyl H NH₂ OH triphosphateacetyl acetyl H NH₂ F triphosphate acetyl acetyl H NH₂ Cl H H H H Cl H HH H H Cl H H H H H Cl NH₂ H H H H Cl NH-cyclopropyl H H H H Cl NH-methylH H H H Cl NH-ethyl H H H H Cl NH-acetyl H H H H Cl OH H H H H Cl OMe HH H H Cl OEt H H H H Cl O-cyclopropyl H H H H Cl O-acetyl H H H H Cl SHH H H H Cl SMe H H H H Cl SEt H H H H Cl S-cyclopropyl monophosphate H HH Cl NH₂ monophosphate H H H Cl NH-acetyl monophosphate H H H ClNH-cyclopropyl monophosphate H H H Cl NH-methyl monophosphate H H H ClNH-ethyl monophosphate H H H Cl OH monophosphate H H H Cl O-acetylmonophosphate H H H Cl OMe monophosphate H H H Cl OEt monophosphate H HH Cl O-cyclopropyl monophosphate H H H Cl SH monophosphate H H H Cl SMemonophosphate H H H Cl SEt monophosphate H H H Cl S-cyclopropyldiphosphate H H H Cl NH₂ diphosphate H H H Cl NH-acetyl diphosphate H HH Cl NH-cyclopropyl diphosphate H H H Cl NH-methyl diphosphate H H H ClNH-ethyl diphosphate H H H Cl OH diphosphate H H H Cl O-acetyldiphosphate H H H Cl OMe diphosphate H H H Cl OEt diphosphate H H H ClO-cyclopropyl diphosphate H H H Cl SH diphosphate H H H Cl SMediphosphate H H H Cl SEt diphosphate H H H Cl S-cyclopropyl triphosphateH H H Cl NH₂ triphosphate H H H Cl NH-acetyl triphosphate H H H ClNH-cyclopropyl triphosphate H H H Cl NH-methyl triphosphate H H H ClNH-ethyl triphosphate H H H Cl OH triphosphate H H H Cl OMe triphosphateH H H Cl OEt triphosphate H H H Cl O-cyclopropyl triphosphate H H H ClO-acetyl triphosphate H H H Cl SH triphosphate H H H Cl SMe triphosphateH H H Cl SEt triphosphate H H H Cl S-cyclopropyl monophosphatemonophosphate monophosphate H Cl NH₂ monophosphate monophosphatemonophosphate H Cl NH-cyclopropyl monophosphate monophosphatemonophosphate H Cl OH diphosphate diphosphate diphosphate H Cl NH₂diphosphate diphosphate diphosphate H Cl NH-cyclopropyl diphosphatediphosphate diphosphate H Cl OH triphosphate triphosphate triphosphate HCl NH₂ triphosphate triphosphate triphosphate H Cl NH-cyclopropyltriphosphate triphosphate triphosphate H Cl OH H H H F Cl NH₂ H H H F ClNH-cyclopropyl H H H F Cl OH H H H Cl Cl NH₂ H H H Cl Cl NH-cyclopropylH H H Cl Cl OH H H H Br Cl NH₂ H H H Br Cl NH-cyclopropyl H H H Br Cl OHH H H NH₂ Cl NH₂ H H H NH₂ Cl NH-cyclopropyl H H H NH₂ Cl OH H H H SH ClNH₂ H H H SH Cl NH-cyclopropyl H H H SH Cl OH acetyl H H H Cl NH₂ acetylH H H Cl NH-cyclopropyl acetyl H H H Cl OH acetyl H H F Cl NH₂ acetyl HH F Cl NH-cyclopropyl acetyl H H F Cl OH H acetyl acetyl H Cl NH₂ Hacetyl acetyl H Cl NH-cyclopropyl H acetyl acetyl H Cl OH acetyl acetylacetyl H Cl NH₂ acetyl acetyl acetyl H Cl NH-cyclopropyl acetyl acetylacetyl H Cl OH monophosphate acetyl acetyl H Cl NH₂ monophosphate acetylacetyl H Cl NH-cyclopropyl monophosphate acetyl acetyl H Cl OHdiphosphate acetyl acetyl H Cl NH₂ diphosphate acetyl acetyl H ClNH-cyclopropyl diphosphate acetyl acetyl H Cl OH triphosphate acetylacetyl H Cl NH₂ triphosphate acetyl acetyl H Cl NH-cyclopropyltriphosphate acetyl acetyl H Cl OH H H H H Cl NH₂ H H H H ClNH-cyclopropyl H H H H Cl OH H H H H Br NH₂ H H H H Br NH-cyclopropyl HH H H Br OH

Alternatively, the following nucleosides of Formula VI are prepared,using the appropriate sugar and pyrimidine or purine bases.

wherein: R¹ R² R³ X¹ Y H H H H H H H H H NH₂ H H H H NH-cyclopropyl H HH H NH-methyl H H H H NH-ethyl H H H H NH-acetyl H H H H OH H H H H OMeH H H H OEt H H H H O-cyclopropyl H H H H O-acetyl H H H H SH H H H HSMe H H H H SEt H H H H S-cyclopropyl monophosphate H H H NH₂monophosphate H H H NH-acetyl monophosphate H H H NH-cyclopropylmonophosphate H H H NH-methyl monophosphate H H H NH-ethyl monophosphateH H H OH monophosphate H H H O-acetyl monophosphate H H H OMemonophosphate H H H OEt monophosphate H H H O-cyclopropyl monophosphateH H H SH monophosphate H H H SMe monophosphate H H H SEt monophosphate HH H S-cyclopropyl diphosphate H H H NH₂ diphosphate H H H NH-acetyldiphosphate H H H NH-cyclopropyl diphosphate H H H NH-methyl diphosphateH H H NH-ethyl diphosphate H H H OH diphosphate H H H O-acetyldiphosphate H H H OMe diphosphate H H H OEt diphosphate H H HO-cyclopropyl diphosphate H H H SH diphosphate H H H SMe diphosphate H HH SEt diphosphate H H H S-cyclopropyl triphosphate H H H NH₂triphosphate H H H NH-acetyl triphosphate H H H NH-cyclopropyltriphosphate H H H NH-methyl triphosphate H H H NH-ethyl triphosphate HH H OH triphosphate H H H OMe triphosphate H H H OEt triphosphate H H HO-cyclopropyl triphosphate H H H O-acetyl triphosphate H H H SHtriphosphate H H H SMe triphosphate H H H SEt triphosphate H H HS-cyclopropyl monophosphate monophosphate monophosphate H NH₂monophosphate monophosphate monophosphate H NH-cyclopropyl monophosphatemonophosphate monophosphate H OH diphosphate diphosphate diphosphate HNH₂ diphosphate diphosphate diphosphate H NH-cyclopropyl diphosphatediphosphate diphosphate H OH triphosphate triphosphate triphosphate HNH₂ triphosphate triphosphate triphosphate H NH-cyclopropyl triphosphatetriphosphate triphosphate H OH H H H F NH₂ H H H F NH-cyclopropyl H H HF OH H H H Cl NH₂ H- H H Cl NH-cyclopropyl H H H Cl OH H H H Br NH₂ H HH Br NH-cyclopropyl H H H Br OH H H H NH₂ NH₂ H H H NH₂ NH-cyclopropyl HH H NH₂ OH H H H SH NH₂ H H H SH NH-cyclopropyl H H H SH OH acetyl H H HNH₂ acetyl H H H NH-cyclopropyl acetyl H H H OH acetyl H H F NH₂ acetylH H F NH-cyclopropyl acetyl H H F OH H acetyl acetyl H NH₂ H acetylacetyl H NH-cyclopropyl H acetyl acetyl H OH acetyl acetyl acetyl H NH₂acetyl acetyl acetyl H NH-cyclopropyl acetyl acetyl acetyl H OHmonophosphate acetyl acetyl H NH₂ monophosphate acetyl acetyl HNH-cyclopropyl monophosphate acetyl acetyl H OH diphosphate acetylacetyl H NH₂ diphosphate acetyl acetyl H NH-cyclopropyl diphosphateacetyl acetyl H OH triphosphate acetyl acetyl H NH₂ triphosphate acetylacetyl H NH-cyclopropyl triphosphate acetyl acetyl H OH

Alternatively, the following nucleosides of Formula XIII are prepared,using the appropriate sugar and pyrimidine or purine bases.

wherein: R¹ R² R³ R⁶ X Base H H H CH₃ O 2,4-O- Diacetyluracil H H H CH₃O Hypoxanthine H H H CH₃ O 2,4-O-Diacetylthymine H H H CH₃ O Thymine H HH CH₃ O Cytosine H H H CH₃ O 4-(N-mono- acetyl)cytosine H H H CH₃ O4-(N,N- diacetyl)cytosine H H H CH₃ O Uracil H H H CH₃ O 5-FluorouracilH H H CH₃ S 2,4-O- Diacetyluraci H H H CH₃ S Hypoxanthine H H H CH₃ S2,4-O- Diacetylthymine H H H CH₃ S Thymine H H H CH₃ S Cytosine H H HCH₃ S 4-(N-mono- acetyl)cytosine H H H CH₃ S 4-(N,N- diacetyl)cytosine HH H CH₃ S Uracil H H H CH₃ S 5-Fluorouracil monophosphate H H CH₃ O2,4-O- Diacetyluracil monophosphate H H CH₃ O Hypoxanthine monophosphateH H CH₃ O 2,4-O- Diacetylthym monophosphate H H CH₃ O Thyminemonophosphate H H CH₃ O Cytosine monophosphate H H CH₃ O 4-(N-mono-acetyl)cytosine monophosphate H H CH₃ O 4-(N,N- diacetyl)cytosinemonophosphate H H CH₃ O Uracil monophosphate H H CH₃ O 5-Fluorouracilmonophosphate H H CH₃ S 2,4-O- Diacetyluracil monophosphate H H CH₃ SHypoxanthine monophosphate H H CH₃ S 2,4-O- Diacetylthym monophosphate HH CH₃ S Thymine monophosphate H H CH₃ S Cytosine monophosphate H H CH₃ S4-(N-mono- acetyl)cytosine monophosphate H H CH₃ S 4-(N,N-diacetyl)cytosine monophosphate H H CH₃ S Uracil monophosphate H H CH₃ S5-Fluorouracil diphosphate H H CH₃ O 2,4-O- Diacetyluracil diphosphate HH CH₃ O Hypoxanthine diphosphate H H CH₃ O 2,4-O- Diacetylthyminediphosphate H H CH₃ O Thymine diphosphate H H CH₃ O Cytosine diphosphateH H CH₃ O 4-(N-mono- acetyl)cytosine diphosphate H H CH₃ O 4-(N,N-diacetyl)cytosine diphosphate H H CH₃ O Uracil diphosphate H H CH₃ O5-Fluorouracil diphosphate H H CH₃ S 2,4-O- Diacetyluracil diphosphate HH CH₃ S Hypoxanthine diphosphate H H CH₃ S 2,4-O- Diacetylthymdiphosphate H H CH₃ S Thymine diphosphate H H CH₃ S Cytosinetriphosphate H H CH₃ O 2,4-O- Diacetyluracil triphosphate H H CH₃ OHypoxanthine triphosphate H H CH₃ O 2,4-O- Diacetylthymine triphosphateH H CH₃ O Thymine triphosphate H H CH₃ O Cytosine triphosphate H H CH₃ O4-(N-mono- acetyl)cytosine triphosphate H H CH₃ O 4-(N,N-diacetyl)cytosine triphosphate H H CH₃ O Uracil triphosphate H H CH₃ O5-Fluorouracil triphosphate H H CH₃ S 2,4-O- Diacetyluracil triphosphateH H CH₃ S Hypoxanthine triphosphate H H CH₃ S 2,4-O- Diacetylthyminetriphosphate H H CH₃ S Thymine triphosphate H H CH₃ S Cytosinemonophosphate monophosphate monophosphate CF₃ O 2,4-O- Diacetyluracilmonophosphate monophosphate monophosphate CF₃ O Hypoxanthinemonophosphate monophosphate monophosphate CF₃ O 2,4-O- Diacetylthyminemonophosphate monophosphate monophosphate CF₃ O Thymine monophosphatemonophosphate monophosphate CF₃ O Cytosine monophosphate monophosphatemonophosphate CF₃ O 4-(N-mono- acetyl)cytosine monophosphatemonophosphate monophosphate CF₃ O 4-(N,N- diacetyl)cytosinemonophosphate monophosphate monophosphate CF₃ O Uracil monophosphatemonophosphate monophosphate CF₃ O 5-Fluorouracil monophosphatemonophosphate monophosphate CF₃ S 2,4-O- Diacetyluracil monophosphatemonophosphate monophosphate CF₃ S Hypoxanthine monophosphatemonophosphate monophosphate CF₃ S 2,4-O- Diacetylthymine monophosphatemonophosphate monophosphate CF₃ S Thymine monophosphate monophosphatemonophosphate CF₃ S Cytosine monophosphate monophosphate monophosphateCF₃ S 4-(N-mono- acetyl)cytosine monophosphate monophosphatemonophosphate CF₃ S 4-(N,N- diacetyl)cytosine monophosphatemonophosphate monophosphate CF₃ S Uracil monophosphate monophosphatemonophosphate CF₃ S 5-Fluorouracil acetyl acetyl acetyl CF₃ O 4-(N,N-diacetyl)cytosine acetyl acetyl acetyl CF₃ S 4-(N,N- diacetyl)cytosineacetyl acetyl acetyl 2-bromo- O 4-(N,N- vinyl diacetyl)cytosine acetylacetyl acetyl 2-bromo- S 4-(N,N- vinyl diacetyl)cytosine H H H CH₃ O2-(N,N-diacetyl)- guanine H H H CH₃ O 6-O-acetyl guanine H H H CH₃ O8-fluoroguanine H H H CH₃ O guanine H H H CH₃ O 6-(N,N-diacetyl)-adenine H H H CH₃ O 2-fluoroadenine H H H CH₃ O 8-fluoroadenine H H HCH₃ O 2,8-difluoro- adenine H H H CH₃ O adenine H H H CH₃ S2-(N,N-diacetyl)- guanine H H H CH₃ S 6-O-acetyl guanine H H H CH₃ S8-fluoroguanine H H H CH₃ S guanine H H H CH₃ S 6-(N,N-diacetyl)-adenine H H H CH₃ S 2-fluoroadenine H H H CH₃ S 8-fluoroadenine H H HCH₃ S 2,8-difluoro- adenine H H H CH₃ S adenine monophosphate H H CH₃ O2-(N,N-diacetyl)- guanine monophosphate H H CH₃ O 6-O-acetyl guaninemonophosphate H H CH₃ O 8-fluoroguanine monophosphate H H CH₃ O guaninemonophosphate H H CH₃ O 6-(N,N-diacetyl)- adenine monophosphate H H CH₃O 2-fluoroadenine monophosphate H H CH₃ O 8-fluoroadenine monophosphateH H CH₃ O 2,8-difluoro- adenine monophosphate H H CH₃ O adeninemonophosphate H H CH₃ S 2-(N,N-diacetyl)- guanine monophosphate H H CH₃S 6-O-acetyl guanine monophosphate H H CH₃ S 8-fluoroguaninemonophosphate H H CH₃ S guanine monophosphate H H CH₃ S6-(N,N-diacetyl)- adenine monophosphate H H CH₃ S 2-fluoroadeninemonophosphate H H CH₃ S 8-fluoroadenine monophosphate H H CH₃ S2,8-difluoro- adenine monophosphate H H CH₃ S adenine diphosphate H HCH₃ O 2-(N,N-diacetyl)- guanine diphosphate H H CH₃ O 6-O-acetyl guaninediphosphate H H CH₃ O 8-fluoroguanine diphosphate H H CH₃ O guaninediphosphate H H CH₃ O 6-(N,N-diacetyl)- adenine diphosphate H H CH₃ O2-fluoroadenine diphosphate H H CH₃ O 8-fluoroadenine diphosphate H HCH₃ O 2,8-difluoro- adenine diphosphate H H CH₃ O adenine diphosphate HH CH₃ S 2-(N,N-diacetyl)- guanine diphosphate H H CH₃ S 6-O-acetylguanine diphosphate H H CH₃ S 8-fluoroguanine diphosphate H H CH₃ Sguanine diphosphate H H CH₃ S 6-(N,N-diacetyl)- adenine diphosphate H HCH₃ S 2-fluoroadenine diphosphate H H CH₃ S 8-fluoroadenine diphosphateH H CH₃ S 2,8-difluoro- adenine diphosphate H H CH₃ S adeninetriphosphate H H CH₃ O 2-(N,N-diacetyl)- guanine triphosphate H H CH₃ O6-O-acetyl guanine triphosphate H H CH₃ O 8-fluoroguanine triphosphate HH CH₃ O guanine triphosphate H H CH₃ O 6-(N,N-diacetyl)- adeninetriphosphate H H CH₃ O 2-fluoroadenine triphosphate H H CH₃ O8-fluoroadenine triphosphate H H CH₃ O 2,8-difluoro- adeninetriphosphate H H CH₃ O 2-(N,N-diacetyl)- guanine triphosphate H H CH₃ S6-O-acetyl guanine triphosphate H H CH₃ S 8-fluoroguanine triphosphate HH CH₃ S guanine triphosphate H H CH₃ S 6-(N,N-diacetyl)- adeninetriphosphate H H CH₃ S 2-fluoroadenine triphosphate H H CH₃ S8-fluoroadenine triphosphate H H CH₃ S 2,8-difluoro- adeninetriphosphate H H CH₃ S adenine monophosphate monophosphate monophosphateCF₃ O 2-(N,N-diacetyl)- guanine monophosphate monophosphatemonophosphate CF₃ O 6-O-acetyl guanine monophosphate monophosphatemonophosphate CF₃ O 8-fluoroguanine monophosphate monophosphatemonophosphate CF₃ O guanine monophosphate monophosphate monophosphateCF₃ O 6-(N,N-diacetyl)- adenine monophosphate monophosphatemonophosphate CF₃ O 2-fluoroadenine monophosphate monophosphatemonophosphate CF₃ O 8-fluoroadenine monophosphate monophosphatemonophosphate CF₃ O 2,8-difluoro- adenine monophosphate monophosphatemonophosphate CF₃ O adenine monophosphate monophosphate monophosphateCF₃ S 2-(N,N-diacetyl)- guanine monophosphate monophosphatemonophosphate CF₃ S 6-O-acetyl guanine monophosphate monophosphatemonophosphate CF₃ S 8-fluoroguanine monophosphate monophosphatemonophosphate CF₃ S guanine monophosphate monophosphate monophosphateCF₃ S 6-(N,N-diacetyl)- adenine monophosphate monophosphatemonophosphate CF₃ S 2-fluoroadenine monophosphate monophosphatemonophosphate CF₃ S 8-fluoroadenine monophosphate monophosphatemonophosphate CF₃ S 2,8-difluoro- adenine monophosphate monophosphatemonophosphate CF₃ S adenine acetyl acetyl acetyl CF₃ O guanine acetylacetyl acetyl CF₃ S guanine acetyl acetyl acetyl 2-bromo- O guaninevinyl acetyl acetyl acetyl 2-bromo- S guanine vinyl

Alternatively, the following nucleosides of Formula XIV are prepared,using the appropriate sugar and pyrimidine or purine bases.

wherein: R¹ R² R⁶ X Base H H CH₃ O 2,4-O-Diacetyluracil H H CH₃ OHypoxanthine H H CH₃ O 2,4-O-Diacetylthymine H H CH₃ O Thymine H H CH₃ OCytosine H H CH₃ O 4-(N-mono-acetyl)cytosine H H CH₃ O4-(N,N-diacetyl)cytosine H H CH₃ O Uracil H H CH₃ O 5-Fluorouracil H HCH₃ S 2,4-O-Diacetyluracil H H CH₃ S Hypoxanthine H H CH₃ S2,4-O-Diacetylthymine H H CH₃ S Thymine H H CH₃ S Cytosine H H CH₃ S4-(N-mono-acetyl)cytosin H H CH₃ S 4-(N,N-diacetyl)cytosine H H CH₃ SUracil H H CH₃ S 5-Fluorouracil monophosphate H CH₃ O2,4-O-Diacetyluracil monophosphate H CH₃ O Hypoxanthine monophosphate HCH₃ O 2,4-O-Diacetylthym monophosphate H CH₃ O Thymine monophosphate HCH₃ O Cytosine monophosphate H CH₃ O 4-(N-mono-acetyl)cytosinemonophosphate H CH₃ O 4-(N,N-diacetyl)cytos monophosphate H CH₃ O Uracilmonophosphate H CH₃ O 5-Fluorouracil monophosphate H CH₃ S2,4-O-Diacetyluracil monophosphate H CH₃ S Hypoxanthine monophosphate HCH₃ S 2,4-O-Diacetylthym monophosphate H CH₃ S Thymine monophosphate HCH₃ S Cytosine monophosphate H CH₃ S 4-(N-mono-acetyl)cytosinemonophosphate H CH₃ S 4-(N,N-diacetyl)cytosine monophosphate H CH₃ SUracil monophosphate H CH₃ S 5-Fluorouracil diphosphate H CH₃ O2,4-O-Diacetyluracil diphosphate H CH₃ O Hypoxanthine diphosphate H CH₃O 2,4-O-Diacetylthymine diphosphate H CH₃ O Thymine diphosphate H CH₃ OCytosine diphosphate H CH₃ O 4-(N-mono-acetyl)cytosine diphosphate H CH₃O 4-(N,N-diacetyl)cytosine diphosphate H CH₃ O Uracil diphosphate H CH₃O 5-Fluorouracil diphosphate H CH₃ S 2,4-O-Diacetyluracil diphosphate HCH₃ S Hypoxanthine diphosphate H CH₃ S 2,4-O-Diacetylthymine diphosphateH CH₃ S Thymine diphosphate H CH₃ S Cytosine triphosphate H CH₃ O2,4-O-Diacetyluracil triphosphate H CH₃ O Hypoxanthine triphosphate HCH₃ O 2,4-O-Diacetylthymine triphosphate H CH₃ O Thymine triphosphate HCH₃ O Cytosine triphosphate H CH₃ O 4-(N-mono-acetyl)cytosinetriphosphate H CH₃ O 4-(N,N-diacetyl)cytosine triphosphate H CH₃ OUracil triphosphate H CH₃ O 5-Fluorouracil triphosphate H CH₃ S2,4-O-Diacetyluracil triphosphate H CH₃ S Hypoxanthine triphosphate HCH₃ S 2,4-O-Diacetylthymine triphosphate H CH₃ S Thymine triphosphate HCH₃ S Cytosine monophosphate monophosphate CF₃ O 2,4-O-Diacetyluracilmonophosphate monophosphate CF₃ O Hypoxanthine monophosphatemonophosphate CF₃ O 2,4-O-Diacetylthymine monophosphate monophosphateCF₃ O Thymine monophosphate monophosphate CF₃ O Cytosine monophosphatemonophosphate CF₃ O 4-(N-mono-acetyl)cytosine monophosphatemonophosphate CF₃ O 4-(N,N-diacetyl)cytosine monophosphate monophosphateCF₃ O Uracil monophosphate monophosphate CF₃ O 5-Fluorouracilmonophosphate monophosphate CF₃ S 2,4-O-Diacetyluracil monophosphatemonophosphate CF₃ S Hypoxanthine monophosphate monophosphate CF₃ S2,4-O-Diacetylthymine monophosphate monophosphate CF₃ S Thyminemonophosphate monophosphate CF₃ S Cytosine monophosphate monophosphateCF₃ S 4-(N-mono-acetyl)cytosine monophosphate monophosphate CF₃ S4-(N,N-diacetyl)cytosine monophosphate monophosphate CF₃ S Uracilmonophosphate monophosphate CF₃ S 5-Fluorouracil acetyl acetyl CF₃ O4-(N,N-diacetyl)cytosine acetyl acetyl CF₃ S 4-(N,N-diacetyl)cytosineacetyl acetyl 2-bromo- O 4-(N,N-diacetyl)cytosine vinyl acetyl acetyl2-bromo- S 4-(N,N-diacetyl)cytosine vinyl

Alternatively, the following nucleosides of Formula XV are prepared,using the appropriate sugar and pyrimidine or purine bases.

wherein: R¹ R⁶ X Base H CH₃ O 2,4-O-Diacetyluracil H CH₃ O HypoxanthineH CH₃ O 2,4-O-Diacetylthymine H CH₃ O Thymine H CH₃ O Cytosine H CH₃ O4-(N-mono-acetyl)cytosine H CH₃ O 4-(N,N-diacetyl)cytosine H CH₃ OUracil H CH₃ O 5-Fluorouracil H CH₃ S 2,4-O-Diacetyluracil H CH₃ SHypoxanthine H CH₃ S 2,4-O-Diacetylthymine H CH₃ S Thymine H CH₃ SCytosine H CH₃ S 4-(N-mono-acetyl)cytosine H CH₃ S4-(N,N-diacetyl)cytosine H CH₃ S Uracil H CH₃ S 5-Fluorouracilmonophosphate CH₃ O 2,4-O-Diacetyluracil monophosphate CH₃ OHypoxanthine monophosphate CH₃ O 2,4-O-Diacetylthymine monophosphate CH₃O Thymine monophosphate CH₃ O Cytosine monophosphate CH₃ O4-(N-mono-acetyl)cytosine monophosphate CH₃ O 4-(N,N-diacetyl)cytosinemonophosphate CH₃ O Uracil monophosphate CH₃ O 5-Fluorouracilmonophosphate CH₃ S 2,4-O-Diacetyluracil monophosphate CH₃ SHypoxanthine monophosphate CH₃ S 2,4-O-Diacetylthymine monophosphate CH₃S Thymine monophosphate CH₃ S Cytosine monophosphate CH₃ S4-(N-mono-acetyl)cytosine monophosphate CH₃ S 4-(N,N-diacetyl)cytosinemonophosphate CH₃ S Uracil monophosphate CH₃ S 5-Fluorouracildiphosphate CH₃ O 2,4-O-Diacetyluracil diphosphate CH₃ O Hypoxanthinediphosphate CH₃ O 2,4-O-Diacetylthymine diphosphate CH₃ O Thyminediphosphate CH₃ O Cytosine diphosphate CH₃ O 4-(N-mono-acetyl)cytosinediphosphate CH₃ O 4-(N,N-diacetyl)cytosine diphosphate CH₃ O Uracildiphosphate CH₃ O 5-Fluorouracil diphosphate CH₃ S 2,4-O-Diacetyluracildiphosphate CH₃ S Hypoxanthine diphosphate CH₃ S 2,4-O-Diacetylthyminediphosphate CH₃ S Thymine diphosphate CH₃ S Cytosine triphosphate CH₃ O2,4-O-Diacetyluracil triphosphate CH₃ O Hypoxanthine triphosphate CH₃ O2,4-O-Diacetylthymine triphosphate CH₃ O Thymine triphosphate CH₃ OCytosine triphosphate CH₃ O 4-(N-mono-acetyl)cytosine triphosphate CH₃ O4-(N,N-diacetyl)cytosine triphosphate CH₃ O Uracil triphosphate CH₃ O5-Fluorouracil triphosphate CH₃ S 2,4-O-Diacetyluracil triphosphate CH₃S Hypoxanthine triphosphate CH₃ S 2,4-O-Diacetylthymine triphosphate CH₃S Thymine triphosphate CH₃ S Cytosine monophosphate CF₃ O2,4-O-Diacetyluracil monophosphate CF₃ O Hypoxanthine monophosphate CF₃O 2,4-O-Diacetylthymine monophosphate CF₃ O Thymine monophosphate CF₃ OCytosine monophosphate CF₃ O 4-(N-mono-acetyl)cytosine monophosphate CF₃O 4-(N,N-diacetyl)cytosine monophosphate CF₃ O Uracil monophosphate CF₃O 5-Fluorouracil monophosphate CF₃ S 2,4-O-Diacetyluracil monophosphateCF₃ S Hypoxanthine monophosphate CF₃ S 2,4-O-Diacetylthyminemonophosphate CF₃ S Thymine monophosphate CF₃ S Cytosine monophosphateCF₃ S 4-(N-mono-acetyl)cytosine monophosphate CF₃ S4-(N,N-diacetyl)cytosine monophosphate CF₃ S Uracil monophosphate CF₃ S5-Fluorouracil acetyl CF₃ O 4-(N,N-diacetyl)cytosine acetyl CF₃ S4-(N,N-diacetyl)cytosine acetyl 2-bromo-vinyl O 4-(N,N-diacetyl)cytosineacetyl 2-bromo-vinyl S 4-(N,N-diacetyl)cytosine

Alternatively, the following nucleosides of Formula XVIII are prepared,using the appropriate sugar and pymidine or purine bases.

wherein: R¹ R⁶ R⁷ X Base R⁸ R⁹ H CH₃ OH O 2,4-O-Diacetyluracil H Me HCH₃ OH O Hypoxanthine H Me H CH₃ OH O 2,4-O-Diacetylthymine H Me H CH₃OH O Thymine H Me H CH₃ OH O Cytosine H Me H CH₃ OH O4-(N-mono-acetyl)cytosine H Me H CH₃ OH O 4-(N,N-diacetyl)cytosine H MeH CH₃ OH O Uracil H Me H CH₃ OH O 5-Fluorouracil H Me H CH₃ OH S2,4-O-Diacetyluracil H Me H CH₃ OH S Hypoxanthine H Me H CH₃ OH S2,4-O-Diacetylthymine H Me H CH₃ OH S Thymine H Me H CH₃ OH S Cytosine HMe H CH₃ OH S 4-(N-mono-acetyl)cytosine H Me H CH₃ OH S4-(N,N-diacetyl)cytosine H Me H CH₃ OH S Uracil H Me H CH₃ OH S5-Fluorouracil H Me monophosphate CH₃ OH O 2,4-O-Diacetyluracil H Memonophosphate CH₃ OH O Hypoxanthine H Me monophosphate CH₃ OH O2,4-O-Diacetylthymine H Me monophosphate CH₃ OH O Thymine H Memonophosphate CH₃ OH O Cytosine H Me monophosphate CH₃ OH O4-(N-mono-acetyl)cytosine H Me monophosphate CH₃ OH O4-(N,N-diacetyl)cytosine H Me monophosphate CH₃ OH O Uracil H Memonophosphate CH₃ OH O 5-Fluorouracil H Me monophosphate CH₃ OH S2,4-O-Diacetyluracil H Me monophosphate CH₃ OH S Hypoxanthine H Memonophosphate CH₃ OH S 2,4-O-Diacetylthymine H Me monophosphate CH₃ OH SThymine H Me monophosphate CH₃ OH S Cytosine H Me monophosphate CH₃ OH S4-(N-mono-acetyl)cytosine H Me monophosphate CH₃ OH S4-(N,N-diacetyl)cytosine H Me monophosphate CH₃ OH S Uracil H Memonophosphate CH₃ OH S 5-Fluorouracil H Me diphosphate CH₃ OH O2,4-O-Diacetyluracil H Me diphosphate CH₃ OH O Hypoxanthine H Mediphosphate CH₃ OH O 2,4-O-Diacetylthymine H Me diphosphate CH₃ OH OThymine H Me diphosphate CH₃ OH O Cytosine H Me diphosphate CH₃ OH O4-(N-mono-acetyl)cytosine H Me diphosphate CH₃ OH O4-(N,N-diacetyl)cytosine H Me diphosphate CH₃ OH O Uracil H Mediphosphate CH₃ OH O 5-Fluorouracil H Me diphosphate CH₃ OH S2,4-O-Diacetyluracil H Me diphosphate CH₃ OH S Hypoxanthine H Mediphosphate CH₃ OH S 2,4-O-Diacetylthymine H Me diphosphate CH₃ OH SThymine H Me diphosphate CH₃ OH S Cytosine H Me triphosphate CH₃ OH O2,4-O-Diacetyluracil H Me triphosphate CH₃ OH O Hypoxanthine H Metriphosphate CH₃ OH O 2,4-O-Diacetylthymine H Me triphosphate CH₃ OH OThymine H Me triphosphate CH₃ OH O Cytosine H Me triphosphate CH₃ OH O4-(N-mono-acetyl)cytosine H Me triphosphate CH₃ OH O4-(N,N-diacetyl)cytosine H Me triphosphate CH₃ OH O Uracil H Metriphosphate CH₃ OH O 5-Fluorouracil H Me triphosphate CH₃ OH S2,4-O-Diacetyluracil H Me triphosphate CH₃ OH S Hypoxanthine H Metriphosphate CH₃ OH S 2,4-O-Diacetylthymine H Me triphosphate CH₃ OH SThymine H Me triphosphate CH₃ OH S Cytosine H Me monophosphate CF₃ OH O2,4-O-Diacetyluracil H Me monophosphate CF₃ OH O Hypoxanthine H Memonophosphate CF₃ OH O 2,4-O-Diacetylthymine H Me monophosphate CF₃ OH OThymine H Me monophosphate CF₃ OH O Cytosine H Me monophosphate CF₃ OH O4-(N-mono-acetyl)cytosine H Me monophosphate CF₃ OH O4-(N,N-diacetyl)cytosine H Me monophosphate CF₃ OH O Uracil H Memonophosphate CF₃ OH O 5-Fluorouracil H Me monophosphate CF₃ OH S2,4-O-Diacetyluracil H Me monophosphate CF₃ OH S Hypoxanthine H Memonophosphate CF₃ OH S 2,4-O-Diacetylthymine H Me monophosphate CF₃ OH SThymine H Me monophosphate CF₃ OH S Cytosine H Me monophosphate CF₃ OH S4-(N-mono-acetyl)cytosine H Me monophosphate CF₃ OH S4-(N,N-diacetyl)cytosine H Me monophosphate CF₃ OH S Uracil H Memonophosphate CF₃ OH S 5-Fluorouracil H Me acetyl CH₃ OH O4-(N,N-diacetyl)cytosine H Br acetyl CH₃ OH S 4-(N,N-diacetyl)cytosine HBrVII. Anti-Hepatitis C Activity

Compounds can exhibit anti-hepatitis C activity by inhibiting HCVpolymerase, by inhibiting other enzymes needed in the replication cycle,or by other pathways. A number of assays have been published to assessthese activities. A general method that assesses the gross increase ofHCV virus in culture is disclosed in U.S. Pat. No. 5,738,985 to Miles etal. In vitro assays have been reported in Ferrari et al., Jnl. of Vir.,73:1649-1654, 1999; Ishii et al., Hepatology, 29:1227-1235,1999; Lohmannet al., Jnl. of Bio. Chem., 274:10807-10815, 1999; and Yamashita et al,Jnl. of Bio. Chem., 273:15479-15486, 1998.

WO 97/12033, filed on Sep. 27, 1996, by Emory University, listing C.Hagedom and A. Reinoldus as inventors, and which claims priority to U.S.Ser. No. 60/004,383, filed on September 1995, describes an HCVpolymerase assay that can be used to evaluate the activity of thecompounds described herein. Another HCV polymerase assay has beenreported by Bartholomeusz, et al., Hepatitis C virus (HCV) RNApolymerase assay using cloned HCV non-structural proteins; AntiviralTherapy 1996:1 (Supp 4) 18-24.

Screens that measure reductions in kinase activity from HCV drugs aredisclosed in U.S. Pat. No. 6,030,785, to Katze et al., U.S. Pat. No.6,010,848 to Delvecchio et al, and U.S. Pat. No. 5,759,795 to Jubin etal. Screens that measure the protease inhibiting activity of proposedHCV drugs are disclosed in U.S. Pat. No. 5,861,267 to Su et al, U.S.Pat. No. 5,739,002 to De Francesco et al, and U.S. Pat. No. 5,597,691 toHoughton et al.

Example 4 Phosphorylation Assay of Nucleoside to Active Triphosphate

To determine the cellular metabolism of the compounds, HepG2 cells wereobtained from the American Type Culture Collection (Rockville, Md.), andwere grown in 225 cm² tissue culture flasks in minimal essential mediumsupplemented with non-essential amino acids, 1% penicillin-streptomycin.The medium was renewed every three days, and the cells were subculturedonce a week. After detachment of the adherent monolayer with a 10 minuteexposure to 30 mL of trypsin-EDTA and three consecutive washes withmedium, confluent HepG2 cells were seeded at a density of 2.5×10⁶ cellsper well in a 6-well plate and exposed to 10 μM of [³H] labeled activecompound (500 dpm/pmol) for the specified time periods. The cells weremaintained at 37° C. under a 5% CO₂ atmosphere. At the selected timepoints, the cells were washed three times with ice-coldphosphate-buffered saline (PBS). Intracellular active compound and itsrespective metabolites were extracted by incubating the cell pelletovernight at −20° C. with 60% methanol followed by extraction with anadditional 20 μL of cold methanol for one hour in an ice bath. Theextracts were then combined, dried under gentle filtered air flow andstored at −20° C. until HPLC analysis. The preliminary results of theHPLC analysis are tabulated in Table 1. TABLE 1 [pmol/million cells]β-D-2′-CH₃- β-D-2′-CH₃- β-D-2′-CH₃- β-D-2′-CH₃- Time (h) riboA-TPriboU-TP riboC-TP riboG-TP 2 33.1 0.40 2.24 ND 4 67.7 1.21 3.99 ND 8 1471.57 9.76 2.85 24 427 6.39 34.9 0.91 30 456 7.18 36.2 3.22 48 288 9.4256.4 6.26

Example 5 Bioavailability Assay in Cynomolgus Monkeys

Within 1 week prior to the study initiation, the cynomolgus monkey wassurgically implanted with a chronic venous catheter and subcutaneousvenous access port (VAP) to facilitate blood collection and underwent aphysical examination including hematology and serum chemistryevaluations and the body weight was recorded. Each monkey (six total),received approximately 250 uCi of ³H activity with each dose of activecompound, namely β-D-2′-CH₃-riboG at a dose level of 10 mg/kg at a doseconcentration of 5 mg/mL, either via an intravenous bolus (3 monkeys,IV), or via oral gavage (3 monkeys, PO). Each dosing syringe was weighedbefore dosing to gravimetrically determine the quantity of formulationadministered. Urine samples were collected via pan catch at thedesignated intervals (approximately 18-0 hours pre-dose, 0-4, 4-8 and8-12 hours post-dosage) and processed. Blood samples were collected aswell (pre-dose, 0.25, 0.5, 1, 2, 3, 6, 8, 12 and 24 hours post-dosage)via the chronic venous catheter and VAP or from a peripheral vessel ifthe chronic venous catheter procedure should not be possible. The bloodand urine samples were analyzed for the maximum concentration (C_(max)),time when the maximum concentration was achieved (T_(max)), area underthe curve (AUC), half life of the dosage concentration (T_(1/2)),clearance (CL), steady state volume and distribution (V_(ss)) andbioavailibility (F), which are tabulated in Tables 2 and 3, andgraphically illustrated in FIGS. 2 and 3, respectively. TABLE 2 OralBioavailability in Monkeys AUC Norm AUC Mean Norm Dose (ng/mL × (ng/mL ×AUC (ng/mL × (mg) h) h/mg) h/mg) F (%) IV Monkey 1 46.44 13614 293.2 IVMonkey 2 24.53 6581 268.3 IV Monkey 3 20.72 6079 293.4 284.9 PO Monkey 129.04 758 26.1 PO Monkey 2 30.93 898 29.0 PO Monkey 3 30.04 1842 61.338.8 13.6

TABLE 3 Experimental Pharmacokinetics of β-D-2′-CH₃-riboG in CynomolgusMonkeys IV PO Dose/Route (mg/kg) 10 10 C_(max) (ng/mL) 6945.6 ± 1886.0217.7 ± 132.1  T_(max) (hr) 0.25 ± 0.00 2.00 ± 1.00  AUC (ng/mL × hr)8758.0 ± 4212.9 1166.0 ± 589.6  T_(1/2) (hr) 7.9 ± 5.4 10.3 ± 4.1  CL(L/hr/kg) 1.28 ± 0.48 V_(ss) (L/kg) 2.09 ± 0.54 F (%) 13.8

Example 6 Bone Marrow Toxicity Assay

Human bone marrow cells were collected from normal healthy volunteersand the mononuclear population was separated by Ficoll-Hypaque gradientcentrifugation as described previously by Sommadossi J-P, Carlisle R.“Toxicity of 3′-azido-3′-deoxythymidine and9-(1,3-dihydroxy-2-propoxymethyl)guanine for normal human hematopoieticprogenitor cells in vitro” Antimicrobial Agents and Chemotherapy 1987;31:452-454; and Sommadossi J-P, Schinazi R F, Chu C K, Xie M-Y.“Comparison of cytotoxicity of the (−)- and (+)-enantiomer of2′,3′-dideoxy-3′-thiacytidine in normal human bone marrow progenitorcells” Biochemical Pharmacology 1992; 44:1921-1925. The culture assaysfor CFU-GM and BFU-E were performed using a bilayer soft agar ormethylcellulose method. Drugs were diluted in tissue culture medium andfiltered. After 14 to 18 days at 37° C. in a humidified atmosphere of 5%CO₂ in air, colonies of greater than 50 cells were counted using aninverted microscope. The results in Table 4 are presented as the percentinhibition of colony formation in the presence of drug compared tosolvent control cultures. TABLE 4 Human Bone Marrow Toxicity CFU-GM andBFU-E Clonogenic Assays IC₅₀ in μM Treatment CFU-GM BFU-E ribavirin ˜5˜1 β-D-2′-CH₃-riboA >100 >100 β-D-2′-CH₃-riboU >100 >100β-D-2′-CH₃-riboC >10 >10 β-D-2′-CH₃-riboG >10 >100

Example 7 Mitochondria Toxicity Assay

HepG2 cells were cultured in 12-well plates as described above andexposed to various concentrations of drugs as taught by Pan-Zhou X-R,Cui L, Zhou X-J, Sommadossi J-P, Darley-Usmer V M. “Differential effectsof antiretroviral nucleoside analogs on mitochondrial function in HepG2cells” Antimicrob Agents Chemother 2000; 44:496-503. Lactic acid levelsin the culture medium after 4 day drug exposure was measured using aBoehringer lactic acid assay kit. Lactic acid levels were normalized bycell number as measured by hemocytometer count. The preliminary resultsfrom this assay are tabulated in Table 5. TABLE 5 Mitochondrial ToxicityStudy (L-lactic acid assay) Conc. (μM) lactate (mg/10⁶ cell) % ofControl Control 2.18 FIAU 10 3.73 170.4 β-D-2′-CH₃-riboC 1 2.52 115.3 102.36 107.9 50 2.26 103.4 100 2.21 101.2

This invention has been described with reference to its preferredembodiments. Variations and modifications of the invention, will beobvious to those skilled in the art from the foregoing detaileddescription of the invention.

1-88. (canceled)
 89. A method for the treatment of a hepatitis C virusinfection in a host, comprising administering an anti-virally effectiveamount of a compound of Formula XVII:

or a pharmaceutically acceptable salt or ester thereof, wherein: Base isa purine; R¹ and R² are independently H; phosphate, a stabilizedphosphate prodrug; acyl; alkyl; sulfonate ester; benzyl, wherein thephenyl group is optionally substituted with one or more substituents; alipid; an amino acid; a carbohydrate; a peptide; a cholesterol; or otherpharmaceutically acceptable leaving group which when administered invivo is capable of providing a compound wherein R¹ and R² areindependently H or phosphate; R⁶ is, hydroxy, alkyl, azido, cyano,alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower alkyl),—O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl), —O(alkenyl),chloro, bromo, fluoro, iodo, NO₂, NH₂, —NH(lower alkyl), —NH(acyl),—N(lower alkyl)₂, or —N(acyl)₂; R⁷ and R⁹ are independently hydrogen,OR², hydroxy, alkyl, azido, cyano, alkenyl, alkynyl, Br-vinyl,—C(O)O(alkyl), —C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl),—O(lower alkyl), —O(alkenyl), chlorine, bromine, iodine, NO₂, NH₂,—NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, or —N(acyl)₂; R¹⁰ is H,alkyl, chlorine, bromine or iodine; alternatively, R⁷ and R⁹, or R⁷ andR¹⁰ can come together to form a bond; and X is O, S, SO₂ or CH₂. 90-129.(canceled)
 130. The method of claim 89 for the treatment of a hepatitisC virus infection in a host, comprising administering an anti-virallyeffective amount of a compound of Formula II:

or a pharmaceutically acceptable salt or ester thereof, wherein: R¹, R²and R³ are independently H; phosphate or a stabilized phosphate prodrug;acyl; alkyl; sulfonate ester; or benzyl, wherein the phenyl group isoptionally substituted with one or more substituents; a lipid; an aminoacid; a carbohydrate; a peptide; cholesterol; or other pharmaceuticallyacceptable leaving group which when administered in vivo is capable ofproviding a compound wherein R¹, R² and R³ are independently H orphosphate; and Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ orSR⁴; X¹ and X² are independently selected from the group consisting ofH, straight chained, branched or cyclic alkyl, CO-alkyl, CO-aryl,CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁴; and R⁴and R⁵ are independently hydrogen, acyl, or alkyl.
 131. The method ofclaim 89 for the treatment of a hepatitis C virus infection in a host,comprising administering an anti-virally effective amount of a compoundof Formula X or XI:

or a pharmaceutically acceptable salt or ester thereof, wherein: Base isa purine; R¹, R² and R³ are independently H; phosphate or a stabilizedphosphate prodrug; acyl; alkyl; sulfonate ester; or benzyl, wherein thephenyl group is optionally substituted; a lipid; an amino acid; acarbohydrate; a peptide; cholesterol; or other pharmaceuticallyacceptable leaving group which when administered in vivo is capable ofproviding a compound wherein R¹, R² and R³ are independently H orphosphate; R⁶ is hydroxy, alkyl, azido, cyano, alkenyl, alkynyl,Br-vinyl, —(O)O(alkyl), —C(O)O(lower alkyl), —O(acyl), —O(lower acyl),—O(alkyl), —O(lower alkyl), —O(alkenyl), chloro, bromo, fluoro, iodo,NO₂, NH₂, —NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, or —N(acyl)₂;R⁷ is hydrogen, OR³, hydroxy, alkyl, azido, cyano, alkenyl, alkynyl,Br-vinyl, —C(O)O(alkyl), —C(O)O(lower alkyl), —O(acyl), —O(lower acyl),—O(alkyl), —O(lower alkyl), —O(alkenyl), chlorine, bromine, iodine, NO₂,NH₂, —NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, or —N(acyl)₂; and Xis O, S, SO₂ or CH₂.
 132. The method of claim 89 for the treatment of ahepatitis C virus infection in a host, wherein, in the compound ofFormula XVII: R¹⁰ is H, alkyl, chlorine, bromine or iodine; R⁷ and R⁹are independently hydrogen, OR², alkyl, alkenyl, alkynyl, Br-vinyl,O-alkenyl, chlorine, bromine, iodine, NO₂, NH₂, —NH(lower alkyl),—NH(acyl), —N(lower alkyl)₂, or —N(acyl)₂; R⁶ is alkyl, chlorine,bromine or iodine; alternatively, R⁷ and R⁹, or R⁸ and R⁹ can cometogether to form a bond; and X is O, S, SO₂ or CH₂.
 133. The method ofclaim 89 wherein R¹ is hydrogen or phosphate.
 134. The method of claim89 wherein R² is hydrogen, acyl or alkyl.
 135. The method of claim 89wherein R⁶ is alkyl.
 136. The method of claim 89 wherein R⁷ and R⁹ areindependently hydrogen, OR², or hydroxy.
 137. The method of claim 89,wherein R⁷is hydroxy.
 138. The method of claim 89 wherein R⁹ is hydroxy.139. The method of claim 89 wherein R⁷ and R⁹ are hydroxy.
 140. Themethod of claim 89 wherein R¹⁰ is hydrogen.
 141. The method of claim 89wherein X is O.
 142. The method of claim 89 wherein R¹ is hydrogen orphosphate; R² is hydrogen, acyl or alkyl; R⁶ is alkyl; R⁷ and R⁹ areindependently hydrogen, OR², or hydroxy; R¹⁰ is hydrogen; and X is O.143. The method of claim 89, wherein the base is a purine selected fromthe group consisting of N⁶-alkylpurines, N⁶-acylpurines (wherein acyl isC(O)(alkyl, aryl, alkylaryl, or arylalkyl), N⁶-benzylpurine,N⁶-halopurine, N⁶-vinylpurine, N⁶-acetylenic purine, N⁶-acyl purine,N⁶-hydroxyalkyl purine, N⁶-thioalkyl purine, N 2-alkylpurines,N²-alkyl-6-thiopurines, N²-alkylpurines, N²-alkyl-6-thiopurines,5-azacytidinyl, guanine, adenine, hypoxanthine, 2,6-diaminopurine, and6-chloropurine.
 144. The method of claim 89 for the treatment of ahepatitis C virus infection in a host, comprising administering anantivirally effective amount of a compound of the structure:

or a pharmaceutically acceptable salt or ester thereof.
 145. The methodof claim 89 for the treatment of a hepatitis c virus infection in ahost, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or ester thereof, wherein R ishydrogen or alkyl.
 146. The method of claim 196, wherein R is methyl,ethyl, propyl, isopropyl, or cyclopropyl.
 147. The method of claim 196,wherein R is butyl, isobutyl, t-butyl, pentyl, cyclopentyl, isopentyl,or neopentyl.
 148. The method of claim 89 for the treatment of ahepatitis C virus infection in a host, comprising administering anantivirally effective amount of a compound of the structure:

or a pharmaceutically acceptable salt or ester thereof.
 149. The methodof claim 89 for the treatment of a hepatitis C virus infection in ahost, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or ester thereof.
 150. The methodof claim 89 for the treatment of a hepatitis C virus infection in ahost, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or ester thereof.
 151. The methodof claim 89 for the treatment of a hepatitis C virus infection in ahost, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or ester thereof.
 152. The methodof claim 89 for the treatment of a hepatitis C virus infection in ahost, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or ester thereof.
 153. The methodof claim 89 for the treatment of a hepatitis C virus infection in ahost, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or ester thereof.
 154. The methodof claim 89 for the treatment of a hepatitis C virus infection in ahost, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or ester thereof.
 155. The methodof claim 89 for the treatment of a hepatitis C virus infection in ahost, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or ester thereof.
 156. The methodof claim 89 for the treatment of a hepatitis C virus infection in ahost, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or ester thereof.
 157. The methodof claim 89 for the treatment of a hepatitis C virus infection in ahost, wherein the purine base is selected from the group consisting of

is methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl,cyclopentyl, isopentyl, or neopentyl.
 158. The method of claim 89,wherein the method comprises administering the compound or apharmaceutically acceptable salt or ester thereof in combination oralternation with a second anti-hepatitis C virus agent.
 159. The methodof claim 158, wherein the second anti-hepatitis C virus agent isselected from the group consisting of consisting of interferon,ribavirin, a protease inhibitor, a thiazolidine derivative, a polymeraseinhibitor, and a helicase inhibitor.
 160. The method of claim 159,wherein the second anti-hepatitis C virus agent is interferon.
 161. Themethod of claim 159, wherein the second anti-hepatitis C virus agent isa protease inhibitor.
 162. The method of claim 159, wherein the secondanti-hepatitis C virus agent is ribavirin.
 163. The method of claim 89,wherein the compound is in the form of a dosage unit.
 164. The method ofclaim 163, wherein the dosage unit contains 50 to 1000 mg of saidcompound.
 165. The method of claim 163, wherein said dosage unit is atablet or capsule.
 166. The method of claim 89, wherein the host is ahuman.
 167. The method of claim 89, wherein the compound is insubstantially pure form.
 168. The method of claim 89, wherein thecompound is at least 90% by weight of the β-D-isomer.
 169. The method ofclaim 89, wherein the compound is at least 95% by weight of theβ-D-isomer.